[PATCH v4 00/10] Add generic support for kdump DT properties

	Hi all,

This patch series adds generic support for parsing DT properties related
to crash dump kernels ("linux,elfcorehdr" and "linux,elfcorehdr" under
the "/chosen" node), makes use of it on arm64, arm32, and (partially)
riscv, and performs a few cleanups.  It is an evolution of the
combination of [1] and [2].

The series consists of 5 parts:
  1. Patches 1-2 prepare (the visibility of) variables used to hold
     information retrieved from the DT properties.
  2. Patches 3-5 add support to the FDT core for parsing the properties.
     This can co-exist safely with architecture-specific parsing, until
     the latter has been removed.
  3. Patch 6 removes the non-standard handling of "linux,elfcorehdr" on
     riscv.
     I think this can be applied independently, as the non-standard
     handling is in v5.13, but upstream riscv kdump support is still
     incomplete.
  4. Patches 7-9 convert arm64 to use the generic handling instead of
     its own implementation.
  5. Patch 10 adds support for kdump properties to arm32.
     The corresponding patch for kexec-tools is "[PATCH] arm: kdump: Add
     DT properties to crash dump kernel's DTB"[3], which is still valid.

Changes compared to the previous versions:
  - Make elfcorehdr_{addr,size} always visible,
  - Add variables for usable memory limitation,
  - Use IS_ENABLED() instead of #ifdef (incl. initrd and arm64),
  - Clarify what architecture-specific code is still responsible for,
  - Add generic support for parsing linux,usable-memory-range,
  - Remove custom linux,usable-memory-range parsing on arm64,
  - Use generic handling on ARM.
  
This has been tested on arm32 and arm64, and compile-tested on riscv64.

Thanks for your comments!

[1] "[PATCH v3] ARM: Parse kdump DT properties"
    https://lore.kernel.org/r/20210317113130.2554368-1-geert+renesas@glider.be/
[2] "[PATCH 0/3] Add generic-support for linux,elfcorehdr and fix riscv"
    https://lore.kernel.org/r/cover.1623780059.git.geert+renesas@glider.be/
[3] "[PATCH] arm: kdump: Add DT properties to crash dump kernel's DTB"
    https://lore.kernel.org/linux-arm-kernel/20200902154129.6358-1-geert+renesas@glider.be/


Geert Uytterhoeven (10):
  crash_dump: Make elfcorehdr_{addr,size} always visible
  memblock: Add variables for usable memory limitation
  of: fdt: Add generic support for parsing elf core headers property
  of: fdt: Add generic support for parsing usable memory range property
  of: fdt: Use IS_ENABLED(CONFIG_BLK_DEV_INITRD) instead of #ifdef
  riscv: Remove non-standard linux,elfcorehdr handling
  arm64: kdump: Remove custom linux,elfcorehdr parsing
  arm64: kdump: Remove custom linux,usable-memory-range parsing
  arm64: kdump: Use IS_ENABLED(CONFIG_CRASH_DUMP) instead of #ifdef
  ARM: Parse kdump DT properties

 Documentation/devicetree/bindings/chosen.txt  | 12 ++--
 .../arm/boot/compressed/fdt_check_mem_start.c | 48 ++++++++++++--
 arch/arm/mm/init.c                            | 30 +++++++++
 arch/arm64/mm/init.c                          | 63 +------------------
 arch/riscv/mm/init.c                          | 20 ------
 drivers/of/fdt.c                              | 63 ++++++++++++++++---
 include/linux/crash_dump.h                    |  7 ++-
 include/linux/memblock.h                      |  6 ++
 mm/memblock.c                                 |  2 +
 9 files changed, 148 insertions(+), 103 deletions(-)

-- 
2.25.1

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Replace the conditional compilation using "#ifdef CONFIG_BLK_DEV_INITRD"
by a check for "IS_ENABLED(CONFIG_BLK_DEV_INITRD)", to increase compile
coverage and to simplify the code.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - New.
---
 drivers/of/fdt.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 1b4dd5418b44b9fb..a98e1bb9c84d9765 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c

@@ -859,7 +859,6 @@ const void * __init of_flat_dt_match_machine(const void *default_match,
 	return best_data;
 }
 
-#ifdef CONFIG_BLK_DEV_INITRD
 static void __early_init_dt_declare_initrd(unsigned long start,
 					   unsigned long end)
 {

@@ -885,6 +884,9 @@ static void __init early_init_dt_check_for_initrd(unsigned long node)
 	int len;
 	const __be32 *prop;
 
+	if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD))
+		return;
+
 	pr_debug("Looking for initrd properties... ");
 
 	prop = of_get_flat_dt_prop(node, "linux,initrd-start", &len);

@@ -903,11 +905,6 @@ static void __init early_init_dt_check_for_initrd(unsigned long node)
 
 	pr_debug("initrd_start=0x%llx  initrd_end=0x%llx\n", start, end);
 }
-#else
-static inline void early_init_dt_check_for_initrd(unsigned long node)
-{
-}
-#endif /* CONFIG_BLK_DEV_INITRD */
 
 /**
  * early_init_dt_check_for_elfcorehdr - Decode elfcorehdr location from flat

-- 
2.25.1

Replace the conditional compilation using "#ifdef CONFIG_CRASH_DUMP" by
a check for "IS_ENABLED(CONFIG_CRASH_DUMP)", to increase compile
coverage and to simplify the code.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - New.
---
 arch/arm64/mm/init.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index f90ba99437c0f3c9..dc2a5b73232843e4 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -124,7 +124,6 @@ static void __init reserve_crashkernel(void)
 }
 #endif /* CONFIG_KEXEC_CORE */
 
-#ifdef CONFIG_CRASH_DUMP
 /*
  * reserve_elfcorehdr() - reserves memory for elf core header
  *

@@ -135,7 +134,7 @@ static void __init reserve_crashkernel(void)
  */
 static void __init reserve_elfcorehdr(void)
 {
-	if (!elfcorehdr_size)
+	if (!IS_ENABLED(CONFIG_CRASH_DUMP) || !elfcorehdr_size)
 		return;
 
 	if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {

@@ -148,11 +147,6 @@ static void __init reserve_elfcorehdr(void)
 	pr_info("Reserving %lldKB of memory at 0x%llx for elfcorehdr\n",
 		elfcorehdr_size >> 10, elfcorehdr_addr);
 }
-#else
-static void __init reserve_elfcorehdr(void)
-{
-}
-#endif /* CONFIG_CRASH_DUMP */
 
 /*
  * Return the maximum physical address for a zone accessible by the given bits

-- 
2.25.1

Add support for parsing the "linux,usable-memory-range" property in the
"/chosen" node to the FDT core code.  This can co-exist safely with the
architecture-specific parsing, until the latter has been removed.

Architecture-specific code still has to make sure the resulting memory
range limitation is applied, if present.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
About the change to chosen.txt: I have a similar change for
schemas/chosen.yaml in dt-schema.

v4:
  - New.
---
 Documentation/devicetree/bindings/chosen.txt |  6 ++---
 drivers/of/fdt.c                             | 24 ++++++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index 5b0b94eb2d04e79d..1cc3aa10dcb10588 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt

@@ -79,9 +79,9 @@ a different secondary CPU release mechanism)
 linux,usable-memory-range
 -------------------------
 
-This property (arm64 only) holds a base address and size, describing a
-limited region in which memory may be considered available for use by
-the kernel. Memory outside of this range is not available for use.
+This property holds a base address and size, describing a limited region in
+which memory may be considered available for use by the kernel. Memory outside
+of this range is not available for use.
 
 This property describes a limitation: memory within this range is only
 valid when also described through another mechanism that the kernel

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index f797d52c5b492cb7..1b4dd5418b44b9fb 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c

@@ -935,6 +935,29 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
 		 elfcorehdr_addr, elfcorehdr_size);
 }
 
+/**
+ * early_init_dt_check_for_usable_mem_range - Decode usable memory range
+ * location from flat tree
+ * @node: reference to node containing usable memory range location ('chosen')
+ */
+static void __init early_init_dt_check_for_usable_mem_range(unsigned long node)
+{
+	const __be32 *prop;
+	int len;
+
+	pr_debug("Looking for usable-memory-range property... ");
+
+	prop = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
+	if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
+		return;
+
+	cap_mem_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
+	cap_mem_size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+	pr_debug("cap_mem_start=%pa cap_mem_size=%pa\n", &cap_mem_addr,
+		 &cap_mem_size);
+}
+
 #ifdef CONFIG_SERIAL_EARLYCON
 
 int __init early_init_dt_scan_chosen_stdout(void)

@@ -1083,6 +1106,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 
 	early_init_dt_check_for_initrd(node);
 	early_init_dt_check_for_elfcorehdr(node);
+	early_init_dt_check_for_usable_mem_range(node);
 
 	/* Retrieve command line */
 	p = of_get_flat_dt_prop(node, "bootargs", &l);

-- 
2.25.1

RISC-V uses platform-specific code to locate the elf core header in
memory.  However, this does not conform to the standard
"linux,elfcorehdr" DT bindings, as it relies on a reserved memory node
with the "linux,elfcorehdr" compatible value, instead of on a
"linux,elfcorehdr" property under the "/chosen" node.

The non-compliant code can just be removed, as the standard behavior is
already implemented by platform-agnostic handling in the FDT core code.

Fixes: 5640975003d0234d ("RISC-V: Add crash kernel support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - No changes.
---
 arch/riscv/mm/init.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 269fc648ef3d84b2..4aa4b6a034086df6 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c

@@ -829,26 +829,6 @@ static void __init reserve_crashkernel(void)
 }
 #endif /* CONFIG_KEXEC_CORE */
 
-#ifdef CONFIG_CRASH_DUMP
-/*
- * We keep track of the ELF core header of the crashed
- * kernel with a reserved-memory region with compatible
- * string "linux,elfcorehdr". Here we register a callback
- * to populate elfcorehdr_addr/size when this region is
- * present. Note that this region will be marked as
- * reserved once we call early_init_fdt_scan_reserved_mem()
- * later on.
- */
-static int __init elfcore_hdr_setup(struct reserved_mem *rmem)
-{
-	elfcorehdr_addr = rmem->base;
-	elfcorehdr_size = rmem->size;
-	return 0;
-}
-
-RESERVEDMEM_OF_DECLARE(elfcorehdr, "linux,elfcorehdr", elfcore_hdr_setup);
-#endif
-
 void __init paging_init(void)
 {
 	setup_bootmem();

-- 
2.25.1

On Wed, 14 Jul 2021 05:50:16 PDT (-0700), geert+renesas@glider.be wrote:

Reviewed-by: Palmer Dabbelt <redacted>
Acked-by: Palmer Dabbelt <redacted>

LMK if you wanted me to take this series, otherwise I'm going to assume 
it's going in via some other tree.

Hi Palmer,

On Tue, Jul 20, 2021 at 5:43 PM Palmer Dabbelt [off-list ref] wrote:

On Wed, 14 Jul 2021 05:50:16 PDT (-0700), geert+renesas@glider.be wrote:

quoted

RISC-V uses platform-specific code to locate the elf core header in
memory.  However, this does not conform to the standard
"linux,elfcorehdr" DT bindings, as it relies on a reserved memory node
with the "linux,elfcorehdr" compatible value, instead of on a
"linux,elfcorehdr" property under the "/chosen" node.

The non-compliant code can just be removed, as the standard behavior is
already implemented by platform-agnostic handling in the FDT core code.

Fixes: 5640975003d0234d ("RISC-V: Add crash kernel support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - No changes.
---
 arch/riscv/mm/init.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 269fc648ef3d84b2..4aa4b6a034086df6 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c

@@ -829,26 +829,6 @@ static void __init reserve_crashkernel(void)
 }
 #endif /* CONFIG_KEXEC_CORE */

-#ifdef CONFIG_CRASH_DUMP
-/*
- * We keep track of the ELF core header of the crashed
- * kernel with a reserved-memory region with compatible
- * string "linux,elfcorehdr". Here we register a callback
- * to populate elfcorehdr_addr/size when this region is
- * present. Note that this region will be marked as
- * reserved once we call early_init_fdt_scan_reserved_mem()
- * later on.
- */
-static int __init elfcore_hdr_setup(struct reserved_mem *rmem)
-{
-     elfcorehdr_addr = rmem->base;
-     elfcorehdr_size = rmem->size;
-     return 0;
-}
-
-RESERVEDMEM_OF_DECLARE(elfcorehdr, "linux,elfcorehdr", elfcore_hdr_setup);
-#endif
-
 void __init paging_init(void)
 {
      setup_bootmem();

Reviewed-by: Palmer Dabbelt <redacted>
Acked-by: Palmer Dabbelt <redacted>

LMK if you wanted me to take this series, otherwise I'm going to assume
it's going in via some other tree.

There will be a v5 of the series in response to the review comments.
But I think this patch can already be applied.

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Remove the architecture-specific code for parsing the
"linux,usable-memory-range" property under the "/chosen" node in DT, as
the platform-agnostic handling in the FDT core code already takes care
of this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - New.
---
 arch/arm64/mm/init.c | 34 +---------------------------------
 1 file changed, 1 insertion(+), 33 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 946e246660f2b180..f90ba99437c0f3c9 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -227,44 +227,12 @@ static int __init early_mem(char *p)
 }
 early_param("mem", early_mem);
 
-static int __init early_init_dt_scan_usablemem(unsigned long node,
-		const char *uname, int depth, void *data)
-{
-	struct memblock_region *usablemem = data;
-	const __be32 *reg;
-	int len;
-
-	if (depth != 1 || strcmp(uname, "chosen") != 0)
-		return 0;
-
-	reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
-	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
-		return 1;
-
-	usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
-	usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
-
-	return 1;
-}
-
-static void __init fdt_enforce_memory_region(void)
-{
-	struct memblock_region reg = {
-		.size = 0,
-	};
-
-	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
-
-	if (reg.size)
-		memblock_cap_memory_range(reg.base, reg.size);
-}
-
 void __init arm64_memblock_init(void)
 {
 	const s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);
 
 	/* Handle linux,usable-memory-range property */
-	fdt_enforce_memory_region();
+	memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
 
 	/* Remove memory above our supported physical address size */
 	memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);

-- 
2.25.1

Make the forward declarations of elfcorehdr_addr and elfcorehdr_size
always available, like is done for phys_initrd_start and
phys_initrd_size.  Code referring to these symbols can then just check
for IS_ENABLED(CONFIG_CRASH_DUMP), instead of requiring conditional
compilation using an #ifdef, thus preparing to increase compile
coverage.

Suggested-by: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - New.
---
 include/linux/crash_dump.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index a5192b718dbe4f9a..ad31893d13d634de 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h

@@ -10,13 +10,14 @@
 
 #include <linux/pgtable.h> /* for pgprot_t */
 
+/* For IS_ENABLED(CONFIG_CRASH_DUMP) */
+extern unsigned long long elfcorehdr_addr;
+extern unsigned long long elfcorehdr_size;
+
 #ifdef CONFIG_CRASH_DUMP
 #define ELFCORE_ADDR_MAX	(-1ULL)
 #define ELFCORE_ADDR_ERR	(-2ULL)
 
-extern unsigned long long elfcorehdr_addr;
-extern unsigned long long elfcorehdr_size;
-
 extern int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size);
 extern void elfcorehdr_free(unsigned long long addr);
 extern ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos);

-- 
2.25.1

On Wed, Jul 14, 2021 at 02:50:11PM +0200, Geert Uytterhoeven wrote:

Seems like these could be needed and no need to hide them, so perhaps 
just move the #ifdef down.

 
-extern unsigned long long elfcorehdr_addr;
-extern unsigned long long elfcorehdr_size;
-
 extern int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size);
 extern void elfcorehdr_free(unsigned long long addr);
 extern ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos);
-- 
2.25.1

There are two methods to specify the location of the elf core headers:
using the "elfcorehdr=" kernel parameter, as handled by generic code in
kernel/crash_dump.c, or using the "linux,elfcorehdr" property under the
"/chosen" node in the Device Tree, as handled by architecture-specific
code in arch/arm64/mm/init.c.

Extend support for "linux,elfcorehdr" to all platforms supporting DT by
adding platform-agnostic handling for parsing this property to the FDT
core code.  This can co-exist safely with the architecture-specific
parsing, until the latter has been removed.

This requires moving the call to of_scan_flat_dt() up, as the code
scanning the "/chosen" node now needs to be aware of the values of
"#address-cells" and "#size-cells".

Architecture-specific code still has to reserve the memory used by the
elf core headers, if present.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
About the change to chosen.txt: I have a similar change for
schemas/chosen.yaml in dt-schema.

v4:
  - Use IS_ENABLED() instead of #ifdef,
  - Clarify what architecture-specific code is still responsible for.
---
 Documentation/devicetree/bindings/chosen.txt |  6 ++--
 drivers/of/fdt.c                             | 34 ++++++++++++++++++--
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index 45e79172a646c537..5b0b94eb2d04e79d 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt

@@ -106,9 +106,9 @@ respectively, of the root node.
 linux,elfcorehdr
 ----------------
 
-This property (currently used only on arm64) holds the memory range,
-the address and the size, of the elf core header which mainly describes
-the panicked kernel's memory layout as PT_LOAD segments of elf format.
+This property holds the memory range, the address and the size, of the elf
+core header which mainly describes the panicked kernel's memory layout as
+PT_LOAD segments of elf format.
 e.g.
 
 / {

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 344f16bb04ccf081..f797d52c5b492cb7 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c

@@ -8,6 +8,7 @@
 
 #define pr_fmt(fmt)	"OF: fdt: " fmt
 
+#include <linux/crash_dump.h>
 #include <linux/crc32.h>
 #include <linux/kernel.h>
 #include <linux/initrd.h>

@@ -908,6 +909,32 @@ static inline void early_init_dt_check_for_initrd(unsigned long node)
 }
 #endif /* CONFIG_BLK_DEV_INITRD */
 
+/**
+ * early_init_dt_check_for_elfcorehdr - Decode elfcorehdr location from flat
+ * tree
+ * @node: reference to node containing elfcorehdr location ('chosen')
+ */
+static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
+{
+	const __be32 *prop;
+	int len;
+
+	if (!IS_ENABLED(CONFIG_CRASH_DUMP))
+		return;
+
+	pr_debug("Looking for elfcorehdr property... ");
+
+	prop = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
+	if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
+		return;
+
+	elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
+	elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+	pr_debug("elfcorehdr_start=0x%llx elfcorehdr_size=0x%llx\n",
+		 elfcorehdr_addr, elfcorehdr_size);
+}
+
 #ifdef CONFIG_SERIAL_EARLYCON
 
 int __init early_init_dt_scan_chosen_stdout(void)

@@ -1055,6 +1082,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 		return 0;
 
 	early_init_dt_check_for_initrd(node);
+	early_init_dt_check_for_elfcorehdr(node);
 
 	/* Retrieve command line */
 	p = of_get_flat_dt_prop(node, "bootargs", &l);

@@ -1199,14 +1227,14 @@ void __init early_init_dt_scan_nodes(void)
 {
 	int rc = 0;
 
+	/* Initialize {size,address}-cells info */
+	of_scan_flat_dt(early_init_dt_scan_root, NULL);
+
 	/* Retrieve various information from the /chosen node */
 	rc = of_scan_flat_dt(early_init_dt_scan_chosen, boot_command_line);
 	if (!rc)
 		pr_warn("No chosen node found, continuing without\n");
 
-	/* Initialize {size,address}-cells info */
-	of_scan_flat_dt(early_init_dt_scan_root, NULL);
-
 	/* Setup memory, calling early_init_dt_add_memory_arch */
 	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
 }

-- 
2.25.1

Remove the architecture-specific code for parsing the "linux,elfcorehdr"
property under the "/chosen" node in DT, as the platform-agnostic
handling in the FDT core code already takes care of this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - s/handlng/parsing/ in patch description.
---
 arch/arm64/mm/init.c | 21 ---------------------
 1 file changed, 21 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 8490ed2917ff2430..946e246660f2b180 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -125,25 +125,6 @@ static void __init reserve_crashkernel(void)
 #endif /* CONFIG_KEXEC_CORE */
 
 #ifdef CONFIG_CRASH_DUMP
-static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
-		const char *uname, int depth, void *data)
-{
-	const __be32 *reg;
-	int len;
-
-	if (depth != 1 || strcmp(uname, "chosen") != 0)
-		return 0;
-
-	reg = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
-	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
-		return 1;
-
-	elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &reg);
-	elfcorehdr_size = dt_mem_next_cell(dt_root_size_cells, &reg);
-
-	return 1;
-}
-
 /*
  * reserve_elfcorehdr() - reserves memory for elf core header
  *

@@ -154,8 +135,6 @@ static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
  */
 static void __init reserve_elfcorehdr(void)
 {
-	of_scan_flat_dt(early_init_dt_scan_elfcorehdr, NULL);
-
 	if (!elfcorehdr_size)
 		return;
 

-- 
2.25.1

Parse the following DT properties in the crash dump kernel, to provide a
modern interface between kexec and the crash dump kernel:
  - linux,elfcorehdr: ELF core header segment, similar to the
    "elfcorehdr=" kernel parameter.
  - linux,usable-memory-range: Usable memory reserved for the crash dump
    kernel.
    This makes the memory reservation explicit.  If present, Linux no
    longer needs to mask the program counter, and rely on the "mem="
    kernel parameter to obtain the start and size of usable memory.

For backwards compatibility, the traditional method to derive the start
of memory is still used if "linux,usable-memory-range" is absent, and
the "elfcorehdr=" and "mem=" kernel parameters are still parsed.

Loosely based on the ARM64 version by Akashi Takahiro.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
The corresponding patch for kexec-tools is "[PATCH] arm: kdump: Add DT
properties to crash dump kernel's DTB", which is still valid:
https://lore.kernel.org/linux-arm-kernel/20200902154129.6358-1-geert+renesas@glider.be/

v4:
  - Remove references to architectures in chosen.txt, to avoid having to
    change this again when more architectures copy kdump support,
  - Remove the architecture-specific code for parsing
    "linux,usable-memory-range" and "linux,elfcorehdr", as the FDT core
    code now takes care of this,
  - Move chosen.txt change to patch changing the FDT core,
  - Use IS_ENABLED(CONFIG_CRASH_DUMP) instead of #ifdef,

v3:
  - Rebase on top of accepted solution for DTB memory information
    handling, which is part of v5.12-rc1,

v2:
  - Rebase on top of reworked DTB memory information handling.
---
 .../arm/boot/compressed/fdt_check_mem_start.c | 48 ++++++++++++++++---
 arch/arm/mm/init.c                            | 30 ++++++++++++
 2 files changed, 72 insertions(+), 6 deletions(-)

diff --git a/arch/arm/boot/compressed/fdt_check_mem_start.c b/arch/arm/boot/compressed/fdt_check_mem_start.c
index 62450d824c3ca180..9291a2661bdfe57f 100644
--- a/arch/arm/boot/compressed/fdt_check_mem_start.c
+++ b/arch/arm/boot/compressed/fdt_check_mem_start.c

@@ -55,16 +55,17 @@ static uint64_t get_val(const fdt32_t *cells, uint32_t ncells)
  * DTB, and, if out-of-range, replace it by the real start address.
  * To preserve backwards compatibility (systems reserving a block of memory
  * at the start of physical memory, kdump, ...), the traditional method is
- * always used if it yields a valid address.
+ * used if it yields a valid address, unless the "linux,usable-memory-range"
+ * property is present.
  *
  * Return value: start address of physical memory to use
  */
 uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt)
 {
-	uint32_t addr_cells, size_cells, base;
+	uint32_t addr_cells, size_cells, usable_base, base;
 	uint32_t fdt_mem_start = 0xffffffff;
-	const fdt32_t *reg, *endp;
-	uint64_t size, end;
+	const fdt32_t *usable, *reg, *endp;
+	uint64_t size, usable_end, end;
 	const char *type;
 	int offset, len;
 

@@ -80,6 +81,27 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt)
 	if (addr_cells > 2 || size_cells > 2)
 		return mem_start;
 
+	/*
+	 * Usable memory in case of a crash dump kernel
+	 * This property describes a limitation: memory within this range is
+	 * only valid when also described through another mechanism
+	 */
+	usable = get_prop(fdt, "/chosen", "linux,usable-memory-range",
+			  (addr_cells + size_cells) * sizeof(fdt32_t));
+	if (usable) {
+		size = get_val(usable + addr_cells, size_cells);
+		if (!size)
+			return mem_start;
+
+		if (addr_cells > 1 && fdt32_ld(usable)) {
+			/* Outside 32-bit address space */
+			return mem_start;
+		}
+
+		usable_base = fdt32_ld(usable + addr_cells - 1);
+		usable_end = usable_base + size;
+	}
+
 	/* Walk all memory nodes and regions */
 	for (offset = fdt_next_node(fdt, -1, NULL); offset >= 0;
 	     offset = fdt_next_node(fdt, offset, NULL)) {

@@ -107,7 +129,20 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt)
 
 			base = fdt32_ld(reg + addr_cells - 1);
 			end = base + size;
-			if (mem_start >= base && mem_start < end) {
+			if (usable) {
+				/*
+				 * Clip to usable range, which takes precedence
+				 * over mem_start
+				 */
+				if (base < usable_base)
+					base = usable_base;
+
+				if (end > usable_end)
+					end = usable_end;
+
+				if (end <= base)
+					continue;
+			} else if (mem_start >= base && mem_start < end) {
 				/* Calculated address is valid, use it */
 				return mem_start;
 			}

@@ -123,7 +158,8 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt)
 	}
 
 	/*
-	 * The calculated address is not usable.
+	 * The calculated address is not usable, or was overridden by the
+	 * "linux,usable-memory-range" property.
 	 * Use the lowest usable physical memory address from the DTB instead,
 	 * and make sure this is a multiple of 2 MiB for phys/virt patching.
 	 */

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 6162a070a4104a26..dfaee199554dda97 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c

@@ -4,6 +4,7 @@
  *
  *  Copyright (C) 1995-2005 Russell King
  */
+#include <linux/crash_dump.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/swap.h>

@@ -221,8 +222,35 @@ void check_cpu_icache_size(int cpuid)
 }
 #endif
 
+/*
+ * reserve_elfcorehdr() - reserves memory for elf core header
+ *
+ * This function reserves the memory occupied by an elf core header
+ * described in the device tree. This region contains all the
+ * information about primary kernel's core image and is used by a dump
+ * capture kernel to access the system memory on primary kernel.
+ */
+static void __init reserve_elfcorehdr(void)
+{
+	if (!IS_ENABLED(CONFIG_CRASH_DUMP) || !elfcorehdr_size)
+		return;
+
+	if (memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)) {
+		pr_warn("elfcorehdr is overlapped\n");
+		return;
+	}
+
+	memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
+
+	pr_info("Reserving %llu KiB of memory at 0x%llx for elfcorehdr\n",
+		elfcorehdr_size >> 10, elfcorehdr_addr);
+}
+
 void __init arm_memblock_init(const struct machine_desc *mdesc)
 {
+	/* Handle linux,usable-memory-range property */
+	memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
+
 	/* Register the kernel text, kernel data and initrd with memblock. */
 	memblock_reserve(__pa(KERNEL_START), KERNEL_END - KERNEL_START);
 

@@ -236,6 +264,8 @@ void __init arm_memblock_init(const struct machine_desc *mdesc)
 
 	early_init_fdt_scan_reserved_mem();
 
+	reserve_elfcorehdr();
+
 	/* reserve memory for DMA contiguous allocations */
 	dma_contiguous_reserve(arm_dma_limit);
 

-- 
2.25.1

On Wed, Jul 14, 2021 at 02:50:20PM +0200, Geert Uytterhoeven wrote:

Can't this be in common code?

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

v4:
  - New.
---
 include/linux/memblock.h | 6 ++++++
 mm/memblock.c            | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index cbf46f56d1053b68..07e2474c4c3901e9 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h

@@ -25,6 +25,12 @@ extern unsigned long max_pfn;
  */
 extern unsigned long long max_possible_pfn;
 
+/*
+ * limited region in which memory may be considered usable by the kernel
+ */
+extern phys_addr_t cap_mem_addr;
+extern phys_addr_t cap_mem_size;
+
 /**
  * enum memblock_flags - definition of memory region attributes
  * @MEMBLOCK_NONE: no special request

diff --git a/mm/memblock.c b/mm/memblock.c
index 0041ff62c584e7e1..66659f2b10ed40ff 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -101,6 +101,8 @@ unsigned long max_low_pfn;
 unsigned long min_low_pfn;
 unsigned long max_pfn;
 unsigned long long max_possible_pfn;
+phys_addr_t cap_mem_addr;
+phys_addr_t cap_mem_size;
 
 static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
 static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_RESERVED_REGIONS] __initdata_memblock;

-- 
2.25.1

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the 
property is present, you want to call it. If the property is not 
present, nothing happens.

Rob

Hi,

On Wed, Jul 14, 2021 at 07:51:01AM -0600, Rob Herring wrote:

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

quoted

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the 
property is present, you want to call it. If the property is not 
present, nothing happens.

For memblock_cap_memory_range() to work properly it should be called after
memory is detected and added to memblock with memblock_add[_node]()

I'm not huge fan of adding more globals to memblock so if such ordering can
be implemented on the DT side it would be great.

I don't see a way to actually enforce this ordering, so maybe we'd want to
add warning in memblock_cap_memory_range() if memblock.memory is empty.
 

Rob

-- 
Sincerely yours,
Mike.

Hi Mike,

On Sun, Jul 18, 2021 at 11:31 AM Mike Rapoport [off-list ref] wrote:

On Wed, Jul 14, 2021 at 07:51:01AM -0600, Rob Herring wrote:

quoted

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

quoted

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the
property is present, you want to call it. If the property is not
present, nothing happens.

I will have a look...

For memblock_cap_memory_range() to work properly it should be called after
memory is detected and added to memblock with memblock_add[_node]()

I'm not huge fan of adding more globals to memblock so if such ordering can
be implemented on the DT side it would be great.

Me neither ;-)

I don't see a way to actually enforce this ordering, so maybe we'd want to
add warning in memblock_cap_memory_range() if memblock.memory is empty.

"linux,usable-memory-range" is optional, and typically used only in
crashdump kernels, so it would be a bad idea to add such a warning.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Hi Geert,

On Mon, Jul 19, 2021 at 08:59:03AM +0200, Geert Uytterhoeven wrote:

Hi Mike,

On Sun, Jul 18, 2021 at 11:31 AM Mike Rapoport [off-list ref] wrote:

quoted

On Wed, Jul 14, 2021 at 07:51:01AM -0600, Rob Herring wrote:

quoted

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

quoted

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the
property is present, you want to call it. If the property is not
present, nothing happens.

I will have a look...

quoted

For memblock_cap_memory_range() to work properly it should be called after
memory is detected and added to memblock with memblock_add[_node]()

I'm not huge fan of adding more globals to memblock so if such ordering can
be implemented on the DT side it would be great.

Me neither ;-)

quoted

I don't see a way to actually enforce this ordering, so maybe we'd want to
add warning in memblock_cap_memory_range() if memblock.memory is empty.

"linux,usable-memory-range" is optional, and typically used only in
crashdump kernels, so it would be a bad idea to add such a warning.

If I remember correctly, memblock_cap_memory_range() was added to support
"linux,usable-memory-range" for crasdump kernels on arm64 and if it would
be called before memory is registered we may silently corrupt the memory
because the crash kernel will see all the memory as available.

So while WARN() maybe too much a pr_warn() seems to me quite appropriate.
 
-- 
Sincerely yours,
Mike.

Hi Mike,

On Tue, Jul 20, 2021 at 7:41 AM Mike Rapoport [off-list ref] wrote:

On Mon, Jul 19, 2021 at 08:59:03AM +0200, Geert Uytterhoeven wrote:

quoted

On Sun, Jul 18, 2021 at 11:31 AM Mike Rapoport [off-list ref] wrote:

quoted

On Wed, Jul 14, 2021 at 07:51:01AM -0600, Rob Herring wrote:

quoted

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

quoted

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the
property is present, you want to call it. If the property is not
present, nothing happens.

I will have a look...

quoted

For memblock_cap_memory_range() to work properly it should be called after
memory is detected and added to memblock with memblock_add[_node]()

I'm not huge fan of adding more globals to memblock so if such ordering can
be implemented on the DT side it would be great.

Me neither ;-)

quoted

I don't see a way to actually enforce this ordering, so maybe we'd want to
add warning in memblock_cap_memory_range() if memblock.memory is empty.

Sorry, I misread "if memblock.memory is empty" as "if capmem is empty".

quoted

"linux,usable-memory-range" is optional, and typically used only in
crashdump kernels, so it would be a bad idea to add such a warning.

If I remember correctly, memblock_cap_memory_range() was added to support
"linux,usable-memory-range" for crasdump kernels on arm64 and if it would
be called before memory is registered we may silently corrupt the memory
because the crash kernel will see all the memory as available.
"
So while WARN() maybe too much a pr_warn() seems to me quite appropriate.

Yes, makes perfect sense now.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

On Wed, Jul 14, 2021 at 3:51 PM Rob Herring [off-list ref] wrote:

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:

quoted

Add two global variables (cap_mem_addr and cap_mem_size) for storing a
base address and size, describing a limited region in which memory may
be considered available for use by the kernel.  If enabled, memory
outside of this range is not available for use.

These variables can by filled by firmware-specific code, and used in
calls to memblock_cap_memory_range() by architecture-specific code.
An example user is the parser of the "linux,usable-memory-range"
property in the DT "/chosen" node.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
This is similar to how the initial ramdisk (phys_initrd_{start,size})
and ELF core headers (elfcorehdr_{addr,size})) are handled.

Does there exist a suitable place in the common memblock code to call
"memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the
property is present, you want to call it. If the property is not
present, nothing happens.

Seems to work fine when called from early_init_dt_scan_nodes().
Hence v5 will no longer need to touch memblock.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds