Re: [PATCH v2 2/4] KVM: MMU: Move accessed/dirty bit checks from rmap_remove() to drop_spte()

Lai Jiangshan
2010-06-07T08:16:30Z

Avi Kivity wrote:
> Since we need to make the check atomic, move it to the place that will
> set the new spte.
>
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
> arch/x86/kvm/mmu.c | 17 +++++++++--------
> 1 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 16cedc9..b5a2d3d 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -620,19 +620,11 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
> struct kvm_rmap_desc *desc;
> struct kvm_rmap_desc *prev_desc;
> struct kvm_mmu_page *sp;
> - pfn_t pfn;
> gfn_t gfn;
> unsigned long *rmapp;
> int i;
>
> - if (!is_rmap_spte(*spte))
> - return;
> sp = page_header(__pa(spte));
> - pfn = spte_to_pfn(*spte);
> - if (*spte & shadow_accessed_mask)
> - kvm_set_pfn_accessed(pfn);
> - if (is_writable_pte(*spte))
> - kvm_set_pfn_dirty(pfn);
> gfn = kvm_mmu_page_get_gfn(sp, spte - sp->spt);
> rmapp = gfn_to_rmap(kvm, gfn, sp->role.level);
> if (!*rmapp) {
> @@ -668,6 +660,15 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
>
> static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)
> {
> + pfn_t pfn;
> +
> + if (!is_rmap_spte(*sptep))
> + return;

Missing __set_spte(sptep, new_spte); ?

> + pfn = spte_to_pfn(*sptep);
> + if (*sptep & shadow_accessed_mask)
> + kvm_set_pfn_accessed(pfn);
> + if (is_writable_pte(*sptep))
> + kvm_set_pfn_dirty(pfn);
> rmap_remove(kvm, sptep);
> __set_spte(sptep, new_spte);
> }