[PATCH v4 1/5] mm/memory-failure: efi: add the LINUX_EFI_POISONED_MEMORY configuration table

[sashiko-bot at kernel.org]

> Hardware-poisoned page frames are tracked only in the running kernel's
> data structures, so a kexec loses them and the next kernel doesn't have
> this information, thus, tripping into them again.
> 
> Add an EFI configuration table to carry that information across kexec.
> 
> It is a bitmap with one bit per EFI_POISON_UNIT_SIZE (2MiB) of physical
> memory starting at phys_base, modeled on the LINUX_EFI_UNACCEPTED_MEMORY
> table, and it rides the EFI system table to every kernel in the chain.
> Basing the bitmap keeps a machine whose RAM starts high from paying for
> the hole below it.
> 
> List the table in the x86 efi_tables[] too, so an SME host maps it
> unencrypted like every other EFI table.
> 
> The Kconfig symbol has no prompt. There is nothing for a user to decide,
> so it is on wherever it can be, and it only costs 64K per TiB of RAM on
> a kernel that already has the EFI stub and MEMORY_FAILURE. It is
> restricted to 64BIT because the unit arithmetic would need div_u64() on
> 32-bit, and there is no 32-bit EFI configuration with MEMORY_FAILURE to
> test that on.
> 
> This is a similar approach as used as unaccepted memory.
> 
> Suggested-by: Kiryl Shutsemau <kas at kernel.org>
> Signed-off-by: Breno Leitao <leitao at debian.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260909-hwpoison-kho-v4-0-359313564495@debian.org?part=1