Re: [PATCH v2] x86/mm: Remove the zapped-entry checks

[Jose A. Perez de Azpillaga]

On 11/5/26 1:03 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
> 
> Zapping a range calls arch_check_zapped_pte() for every batch of PTEs,
> which is every page for small folios, and arch_check_zapped_pmd() or
> arch_check_zapped_pud() for every huge leaf. Only x86 implements them, as
> out-of-line functions that warn about a shadow stack entry (Write=0,
> Dirty=1) in a VMA without VM_SHADOW_STACK.
> 
> The warning is a VM_WARN_ON_ONCE(), so without CONFIG_DEBUG_VM the
> functions are empty, but the calls remain. With the SRSO "Safe RET"
> mitigation the return of every such call mispredicts.
> 
> The x86 helpers already keep such entries out of other VMAs.
> pte_wrprotect(), pte_mkdirty(), pte_modify() and their PMD versions go
> through SavedDirty, and only pte_mkwrite() and pmd_mkwrite() on a
> VM_SHADOW_STACK VMA create the combination.

makes sense to me.

Reviewed-by: Jose A. Perez de Azpillaga <azpijr@xxxxxxxxx>

-- 
cheers,
jose a. p-a