| Message ID | 20210209170111.4770-1-yu.c.zhang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] KVM: x86/MMU: Do not check unsync status for root SP. | expand |
Sorry, forget the change log: Changes in V3: - fixed a bug in warnings inside mmu_sync_children(). - commit message changes based on Paolo's suggestion. - added Co-developed-by: Sean Christopherson <seanjc@google.com> Changes in V2: - warnings added based on Sean's suggestion. On Wed, Feb 10, 2021 at 01:01:11AM +0800, Yu Zhang wrote: > In shadow page table, only leaf SPs may be marked as unsync; > instead, for non-leaf SPs, we store the number of unsynced > children in unsync_children. Therefore, in kvm_mmu_sync_root(), > sp->unsync shall always be zero for the root SP and there is > no need to check it. Remove the check, and add a warning > inside mmu_sync_children() to assert that the flags are used > properly. > > While at it, move the warning from mmu_need_write_protect() > to kvm_unsync_page(). > > Co-developed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com> > --- > arch/x86/kvm/mmu/mmu.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 86af58294272..5f482af125b4 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, > LIST_HEAD(invalid_list); > bool flush = false; > > + /* > + * Only 4k SPTEs can directly be made unsync, the parent pages > + * should never be unsyc'd. > + */ > + WARN_ON_ONCE(parent->unsync); > + > while (mmu_unsync_walk(parent, &pages)) { > bool protected = false; > > @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); > > static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) > { > + WARN_ON(sp->role.level != PG_LEVEL_4K); > + > trace_kvm_mmu_unsync_page(sp); > ++vcpu->kvm->stat.mmu_unsync; > sp->unsync = 1; > @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, > if (sp->unsync) > continue; > > - WARN_ON(sp->role.level != PG_LEVEL_4K); > kvm_unsync_page(vcpu, sp); > } > > @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) > * mmu_need_write_protect() describe what could go wrong if this > * requirement isn't satisfied. > */ > - if (!smp_load_acquire(&sp->unsync) && > - !smp_load_acquire(&sp->unsync_children)) > + if (!smp_load_acquire(&sp->unsync_children)) > return; > > write_lock(&vcpu->kvm->mmu_lock); > -- > 2.17.1 >
On 09/02/21 18:01, Yu Zhang wrote: > In shadow page table, only leaf SPs may be marked as unsync; > instead, for non-leaf SPs, we store the number of unsynced > children in unsync_children. Therefore, in kvm_mmu_sync_root(), > sp->unsync shall always be zero for the root SP and there is > no need to check it. Remove the check, and add a warning > inside mmu_sync_children() to assert that the flags are used > properly. > > While at it, move the warning from mmu_need_write_protect() > to kvm_unsync_page(). > > Co-developed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com> > --- > arch/x86/kvm/mmu/mmu.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 86af58294272..5f482af125b4 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, > LIST_HEAD(invalid_list); > bool flush = false; > > + /* > + * Only 4k SPTEs can directly be made unsync, the parent pages > + * should never be unsyc'd. > + */ > + WARN_ON_ONCE(parent->unsync); > + > while (mmu_unsync_walk(parent, &pages)) { > bool protected = false; > > @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); > > static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) > { > + WARN_ON(sp->role.level != PG_LEVEL_4K); > + > trace_kvm_mmu_unsync_page(sp); > ++vcpu->kvm->stat.mmu_unsync; > sp->unsync = 1; > @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, > if (sp->unsync) > continue; > > - WARN_ON(sp->role.level != PG_LEVEL_4K); > kvm_unsync_page(vcpu, sp); > } > > @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) > * mmu_need_write_protect() describe what could go wrong if this > * requirement isn't satisfied. > */ > - if (!smp_load_acquire(&sp->unsync) && > - !smp_load_acquire(&sp->unsync_children)) > + if (!smp_load_acquire(&sp->unsync_children)) > return; > > write_lock(&vcpu->kvm->mmu_lock); > Queued, thanks. Paolo
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 86af58294272..5f482af125b4 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, LIST_HEAD(invalid_list); bool flush = false; + /* + * Only 4k SPTEs can directly be made unsync, the parent pages + * should never be unsyc'd. + */ + WARN_ON_ONCE(parent->unsync); + while (mmu_unsync_walk(parent, &pages)) { bool protected = false; @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { + WARN_ON(sp->role.level != PG_LEVEL_4K); + trace_kvm_mmu_unsync_page(sp); ++vcpu->kvm->stat.mmu_unsync; sp->unsync = 1; @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, if (sp->unsync) continue; - WARN_ON(sp->role.level != PG_LEVEL_4K); kvm_unsync_page(vcpu, sp); } @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu) * mmu_need_write_protect() describe what could go wrong if this * requirement isn't satisfied. */ - if (!smp_load_acquire(&sp->unsync) && - !smp_load_acquire(&sp->unsync_children)) + if (!smp_load_acquire(&sp->unsync_children)) return; write_lock(&vcpu->kvm->mmu_lock);