| Message ID | 20200622191850.8529-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Don't put invalid SPs back on the list of active pages | expand |
On 22/06/20 21:18, Sean Christopherson wrote: > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index fdd05c233308..fa5bd3f987dd 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2757,10 +2757,13 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, > if (!sp->root_count) { > /* Count self */ > (*nr_zapped)++; > - list_move(&sp->link, invalid_list); > + if (sp->role.invalid) > + list_add(&sp->link, invalid_list); > + else > + list_move(&sp->link, invalid_list); It's late here, but I think this part needs a comment anyway... Paolo
On Tue, Jun 23, 2020 at 02:23:53AM +0200, Paolo Bonzini wrote: > On 22/06/20 21:18, Sean Christopherson wrote: > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index fdd05c233308..fa5bd3f987dd 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -2757,10 +2757,13 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, > > if (!sp->root_count) { > > /* Count self */ > > (*nr_zapped)++; > > - list_move(&sp->link, invalid_list); > > + if (sp->role.invalid) > > + list_add(&sp->link, invalid_list); > > + else > > + list_move(&sp->link, invalid_list); > > It's late here, but I think this part needs a comment anyway... No argument here. I'll spin a v2, I just realized there is a separate optimization that can build on this patch. I was planning on sending it separately, but I misread the loop in make_mmu_pages_available().
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index fdd05c233308..fa5bd3f987dd 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2757,10 +2757,13 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm, if (!sp->root_count) { /* Count self */ (*nr_zapped)++; - list_move(&sp->link, invalid_list); + if (sp->role.invalid) + list_add(&sp->link, invalid_list); + else + list_move(&sp->link, invalid_list); kvm_mod_used_mmu_pages(kvm, -1); } else { - list_move(&sp->link, &kvm->arch.active_mmu_pages); + list_del(&sp->link); /* * Obsolete pages cannot be used on any vCPUs, see the comment @@ -5732,12 +5735,11 @@ static void kvm_zap_obsolete_pages(struct kvm *kvm) break; /* - * Skip invalid pages with a non-zero root count, zapping pages - * with a non-zero root count will never succeed, i.e. the page - * will get thrown back on active_mmu_pages and we'll get stuck - * in an infinite loop. + * Invalid pages should never land back on the list of active + * pages. Skip the bogus page, otherwise we'll get stuck in an + * infinite loop if the page gets put back on the list (again). */ - if (sp->role.invalid && sp->root_count) + if (WARN_ON(sp->role.invalid)) continue; /* @@ -6015,7 +6017,7 @@ void kvm_mmu_zap_all(struct kvm *kvm) spin_lock(&kvm->mmu_lock); restart: list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) { - if (sp->role.invalid && sp->root_count) + if (WARN_ON(sp->role.invalid)) continue; if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign)) goto restart;
Delete a shadow page from the invalidation list instead of throwing it back on the list of active pages when it's a root shadow page with active users. Invalid active root pages will be explicitly freed by mmu_free_root_page() when the root_count hits zero, i.e. they don't need to be put on the active list to avoid leakage. Use sp->role.invalid to detect that a shadow page has already been zapped, i.e. is not on a list. WARN if an invalid page is encountered when zapping pages, as it should now be impossible. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/mmu/mmu.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)