Re: [PATCH 5.15.y 6/6] KVM: x86/mmu: Rename __direct_map() to direct_map()

Hi Sasha,

On 2026/07/31 4:29, Sasha Levin wrote:
> From: David Matlack <[email protected]>
> 
> [ Upstream commit 6c882ef4fc7bd99b67ad152e75428b669281c521 ]
> 
> Rename __direct_map() to direct_map() since the leading underscores are
> unnecessary. This also makes the page fault handler names more
> consistent: kvm_tdp_mmu_page_fault() calls kvm_tdp_mmu_map() and
> direct_page_fault() calls direct_map().
> 
> Opportunistically make some trivial cleanups to comments that had to be
> modified anyway since they mentioned __direct_map(). Specifically, use
> "()" when referring to functions, and include kvm_tdp_mmu_map() among
> the various callers of disallowed_hugepage_adjust().
> 
> No functional change intended.
> 
> Signed-off-by: David Matlack <[email protected]>
> Reviewed-by: Isaku Yamahata <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> Message-Id: <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> Stable-dep-of: 2abd5287f083 ("KVM: x86: Check for invalid/obsolete root *after* making MMU pages available")

Maybe I'm missing something, but commit 2abd5287f083 ("KVM: x86: Check for
invalid/obsolete root *after* making MMU pages available") cannot be backported
as-is. It depends on is_page_fault_stale(), introduced by commit a955cad84cda
("KVM: x86/mmu: Retry page fault if root is invalidated by memslot update"),
which is missing in 5.15.y.

Furthermore, a955cad84cda is required to fix a regression in 5.15.y when
applying the CVE-2026-46113 and CVE-2026-53359 fixes, but its backport remains
pending [1][2].

I plan to send a manual backport of a955cad84cda and 2abd5287f083.
In doing so, the interface of is_page_fault_stale() will end up incompatible
with mainline. While not ideal, making the interface compatible requires 
struct kvm_page_fault and its 50+ prerequisite commits.

[1] https://lore.kernel.org/all/[email protected]/
[2] https://lore.kernel.org/all/CABgObfaKqT0gMUB_XRP5DW5HmpgaoTgmD-A8_zQVG2Vp5xZE4g@mail.gmail.com/

Thanks,
akagi

> Signed-off-by: Sasha Levin <[email protected]>
> ---
>  arch/x86/kvm/mmu/mmu.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 04e814816b17..c274ab0ceff9 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2991,11 +2991,11 @@ void disallowed_hugepage_adjust(u64 spte, gfn_t gfn, int cur_level,
>  	    is_shadow_present_pte(spte) &&
>  	    !is_large_pte(spte)) {
>  		/*
> -		 * A small SPTE exists for this pfn, but FNAME(fetch)
> -		 * and __direct_map would like to create a large PTE
> -		 * instead: just force them to go down another level,
> -		 * patching back for them into pfn the next 9 bits of
> -		 * the address.
> +		 * A small SPTE exists for this pfn, but FNAME(fetch),
> +		 * direct_map(), or kvm_tdp_mmu_map() would like to create a
> +		 * large PTE instead: just force them to go down another level,
> +		 * patching back for them into pfn the next 9 bits of the
> +		 * address.
>  		 */
>  		u64 page_mask = KVM_PAGES_PER_HPAGE(level) -
>  				KVM_PAGES_PER_HPAGE(level - 1);
> @@ -3004,9 +3004,9 @@ void disallowed_hugepage_adjust(u64 spte, gfn_t gfn, int cur_level,
>  	}
>  }
>  
> -static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> -			int map_writable, int max_level, kvm_pfn_t pfn,
> -			bool prefault, bool is_tdp)
> +static int direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> +		      int map_writable, int max_level, kvm_pfn_t pfn,
> +		      bool prefault, bool is_tdp)
>  {
>  	bool nx_huge_page_workaround_enabled = is_nx_huge_page_enabled();
>  	bool write = error_code & PFERR_WRITE_MASK;
> @@ -4037,8 +4037,8 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
>  	if (r)
>  		goto out_unlock;
>  
> -	r = __direct_map(vcpu, gpa, error_code, map_writable, max_level, pfn,
> -			 prefault, is_tdp);
> +	r = direct_map(vcpu, gpa, error_code, map_writable, max_level, pfn,
> +		       prefault, is_tdp);
>  
>  out_unlock:
>  	write_unlock(&vcpu->kvm->mmu_lock);
> -- 
> 2.53.0
> 
> 
>