On 3/20/23 18:44, Mike Rapoport wrote:

On Mon, Mar 20, 2023 at 11:54:14AM +0100, Alexandre Ghiti wrote:

quoted

Hi Mike,

On 3/16/23 21:12, Mike Rapoport wrote:

quoted

Hi Alexandre,

On Thu, Mar 16, 2023 at 02:17:09PM +0100, Alexandre Ghiti wrote:

quoted

This function allows to split a region in memblock.memory and will be
useful when setting up the linear mapping with STRICT_KERNEL_RWX: it
allows to isolate the kernel text/rodata and then avoid to map those
regions with a PUD/P4D/PGD.

Sorry I've missed it last time. The changelog is fine in the context of

No worries :)

quoted

this series, but if you look at it as a part of memblock changelog it
doesn't provide enough background on why memblock_isolate_memory() is
useful.

Can you please add more context so it would be self explanatory?

What about: "memblock.memory contains the list of memory regions and a
memory region can cover memory that will be mapped with different
permissions. So to ease the mapping process, allow to isolate those regions
by introducing a new function called memblock_isolate_memory. This will be
used in arch specific code to isolate the kernel text/rodata regions when
STRICT_KERNEL_RWX is enabled so that we avoid mapping them with PUD/P4D/PGD
mappings."

With this change

... STRICT_KERNEL_RWX is enabled so that they can be mapped with base pages.

Actually they will get mapped with PMD mappings :) I'll just append: "or 
PMD mapping" to your sentence above if that's ok with you.

Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>

Thanks for your review,

Alex

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Thanks,

Alex

quoted

quoted

Signed-off-by: Alexandre Ghiti <redacted>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Anup Patel <anup@brainfault.org>
---
   include/linux/memblock.h |  1 +
   mm/memblock.c            | 20 ++++++++++++++++++++
   2 files changed, 21 insertions(+)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 50ad19662a32..2f7ef97c0da7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h

@@ -125,6 +125,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
   int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
   int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
   int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
+int memblock_isolate_memory(phys_addr_t base, phys_addr_t size);
   void memblock_free_all(void);
   void memblock_free(void *ptr, size_t size);

diff --git a/mm/memblock.c b/mm/memblock.c
index 25fd0626a9e7..e8c651a37012 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -805,6 +805,26 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
   	return 0;
   }
+/**
+ * memblock_isolate_memory - isolate given range in memblock.memory
+ * @base: base of range to isolate
+ * @size: size of range to isolate
+ *
+ * Isolates the given range in memblock.memory so that it does not share any
+ * region with other ranges.
+ *
+ * Return:
+ * 0 on success, -errno on failure.
+ */
+
+int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
+{
+	int start_rgn, end_rgn;
+
+	return memblock_isolate_range(&memblock.memory, base, size,
+				      &start_rgn, &end_rgn);
+}
+
   static int __init_memblock memblock_remove_range(struct memblock_type *type,
   					  phys_addr_t base, phys_addr_t size)
   {

-- 
2.37.2