[PATCH v5 2/5] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo

vabits_actual variable on arm64 indicates the actual VA space size,
and allows a single binary to support both 48-bit and 52-bit VA
spaces.

If the ARMv8.2-LVA optional feature is present, and we are running
with a 64KB page size; then it is possible to use 52-bits of address
space for both userspace and kernel addresses. However, any kernel
binary that supports 52-bit must also be able to fall back to 48-bit
at early boot time if the hardware feature is not present.

Since TCR_EL1.T1SZ indicates the size offset of the memory region
addressed by TTBR1_EL1 (and hence can be used for determining the
vabits_actual value) it makes more sense to export the same in
vmcoreinfo rather than vabits_actual variable, as the name of the
variable can change in future kernel versions, but the architectural
constructs like TCR_EL1.T1SZ can be used better to indicate intended
specific fields to user-space.

User-space utilities like makedumpfile and crash-utility, need to
read/write this value from/to vmcoreinfo for determining if a virtual
address lies in the linear map range.

The user-space computation for determining whether an address lies in
the linear map range is the same as we have in kernel-space:

  #define __is_lm_address(addr)	(!(((u64)addr) & BIT(vabits_actual - 1)))

I have sent out user-space patches for makedumpfile and crash-utility
to add features for obtaining vabits_actual value from TCR_EL1.T1SZ (see
[0] and [1]).

Akashi reported that he was able to use this patchset and the user-space
changes to get user-space working fine with the 52-bit kernel VA
changes (see [2]).

[0]. http://lists.infradead.org/pipermail/kexec/2019-November/023966.html
[1]. http://lists.infradead.org/pipermail/kexec/2019-November/024006.html
[2]. http://lists.infradead.org/pipermail/kexec/2019-November/023992.html

Cc: James Morse <james.morse@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <redacted>
Cc: Dave Anderson <redacted>
Cc: Kazuhito Hagio <redacted>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: Bhupesh Sharma <redacted>
---
 arch/arm64/include/asm/pgtable-hwdef.h | 1 +
 arch/arm64/kernel/crash_core.c         | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index d9fbd433cc17..d2e7aff5821e 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h

@@ -215,6 +215,7 @@
 #define TCR_TxSZ(x)		(TCR_T0SZ(x) | TCR_T1SZ(x))
 #define TCR_TxSZ_WIDTH		6
 #define TCR_T0SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T0SZ_OFFSET)
+#define TCR_T1SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T1SZ_OFFSET)
 
 #define TCR_EPD0_SHIFT		7
 #define TCR_EPD0_MASK		(UL(1) << TCR_EPD0_SHIFT)

diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c
index ca4c3e12d8c5..f78310ba65ea 100644
--- a/arch/arm64/kernel/crash_core.c
+++ b/arch/arm64/kernel/crash_core.c

@@ -7,6 +7,13 @@
 #include <linux/crash_core.h>
 #include <asm/memory.h>
 
+static inline u64 get_tcr_el1_t1sz(void);
+
+static inline u64 get_tcr_el1_t1sz(void)
+{
+	return (read_sysreg(tcr_el1) & TCR_T1SZ_MASK) >> TCR_T1SZ_OFFSET;
+}
+
 void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_NUMBER(VA_BITS);

@@ -15,5 +22,7 @@ void arch_crash_save_vmcoreinfo(void)
 						kimage_voffset);
 	vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
 						PHYS_OFFSET);
+	vmcoreinfo_append_str("NUMBER(tcr_el1_t1sz)=0x%llx\n",
+						get_tcr_el1_t1sz());
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
 }

-- 
2.7.4

Fix a simple typo in arm64/memory.rst

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <redacted>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Bhupesh Sharma <redacted>
---
 Documentation/arm64/memory.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/arm64/memory.rst b/Documentation/arm64/memory.rst
index 02e02175e6f5..cf03b3290800 100644
--- a/Documentation/arm64/memory.rst
+++ b/Documentation/arm64/memory.rst

@@ -129,7 +129,7 @@ this logic.
 
 As a single binary will need to support both 48-bit and 52-bit VA
 spaces, the VMEMMAP must be sized large enough for 52-bit VAs and
-also must be sized large enought to accommodate a fixed PAGE_OFFSET.
+also must be sized large enough to accommodate a fixed PAGE_OFFSET.
 
 Most code in the kernel should not need to consider the VA_BITS, for
 code that does need to know the VA size the variables are

-- 
2.7.4

Add documentation for 'MAX_PHYSMEM_BITS' variable being added to
vmcoreinfo.

'MAX_PHYSMEM_BITS' defines the maximum supported physical address
space memory.

Cc: Boris Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <redacted>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Anderson <redacted>
Cc: Kazuhito Hagio <redacted>
Cc: x86@kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: Bhupesh Sharma <redacted>
---
 Documentation/admin-guide/kdump/vmcoreinfo.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 007a6b86e0ee..447b64314f56 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst

@@ -93,6 +93,11 @@ It exists in the sparse memory mapping model, and it is also somewhat
 similar to the mem_map variable, both of them are used to translate an
 address.
 
+MAX_PHYSMEM_BITS
+----------------
+
+Defines the maximum supported physical address space memory.
+
 page
 ----
 

-- 
2.7.4

Add documentation for TCR_EL1.T1SZ variable being added to
vmcoreinfo.

It indicates the size offset of the memory region addressed by TTBR1_EL1
and hence can be used for determining the vabits_actual value.

Cc: James Morse <james.morse@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steve Capper <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <redacted>
Cc: Dave Anderson <redacted>
Cc: Kazuhito Hagio <redacted>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Signed-off-by: Bhupesh Sharma <redacted>
---
 Documentation/admin-guide/kdump/vmcoreinfo.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 447b64314f56..f9349f9d3345 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst

@@ -398,6 +398,12 @@ KERNELOFFSET
 The kernel randomization offset. Used to compute the page offset. If
 KASLR is disabled, this value is zero.
 
+TCR_EL1.T1SZ
+------------
+
+Indicates the size offset of the memory region addressed by TTBR1_EL1
+and hence can be used for determining the vabits_actual value.
+
 arm
 ===
 

-- 
2.7.4

On Fri, Nov 29, 2019 at 01:55:14AM +0530, Bhupesh Sharma wrote:

Why is this a separate patch?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette