2022-05-23 07:01:00

by Huang, Shaoqin

Subject: [PATCH] KVM: x86/mmu: Check every prev_roots in __kvm_mmu_free_obsolete_roots()

From: Shaoqin Huang <[email protected]>

Iterate every prev_roots and only zap obsoleted roots.

Signed-off-by: Shaoqin Huang <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 45e1573f8f1d..22803916a609 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5168,7 +5168,7 @@ static void __kvm_mmu_free_obsolete_roots(struct kvm *kvm, struct kvm_mmu *mmu)
roots_to_free |= KVM_MMU_ROOT_CURRENT;

for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
- if (is_obsolete_root(kvm, mmu->root.hpa))
+ if (is_obsolete_root(kvm, mmu->prev_roots.hpa))
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
}

--
2.30.2

2022-05-23 16:18:34

by Sean Christopherson

Subject: Re: [PATCH] KVM: x86/mmu: Check every prev_roots in __kvm_mmu_free_obsolete_roots()

On Sun, May 22, 2022, [email protected] wrote:
> From: Shaoqin Huang <[email protected]>
>
> Iterate every prev_roots and only zap obsoleted roots.

Better would be something like:

When freeing obsolete previous roots, check prev_roots as intended, not
the current root.

Ugh, my bad. This escaped into v5.18 :-(

Fixes: 527d5cd7eece ("KVM: x86/mmu: Zap only obsolete roots if a root shadow page is zapped")
Cc: [email protected]

>
> Signed-off-by: Shaoqin Huang <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 45e1573f8f1d..22803916a609 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5168,7 +5168,7 @@ static void __kvm_mmu_free_obsolete_roots(struct kvm *kvm, struct kvm_mmu *mmu)
> roots_to_free |= KVM_MMU_ROOT_CURRENT;
>
> for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
> - if (is_obsolete_root(kvm, mmu->root.hpa))
> + if (is_obsolete_root(kvm, mmu->prev_roots.hpa))

My version is bad, but at least it compiles ;-)

arch/x86/kvm/mmu/mmu.c: In function ‘__kvm_mmu_free_obsolete_roots’:
arch/x86/kvm/mmu/mmu.c:5182:58: error: ‘(struct kvm_mmu_root_info *)&mmu->prev_roots’ is a pointer; did you mean to use ‘->’?
5182 | if (is_obsolete_root(kvm, mmu->prev_roots.hpa))
| ^
| ->


if (is_obsolete_root(kvm, mmu->prev_roots[i].hpa))

> roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
> }
>
> --
> 2.30.2
>