When this was introduced, kvm_flush_remote_tlbs() could be called without holding mmu_lock. It is now acknowledged that the function must be called before releasing mmu_lock, and all callers have already been changed to do so.
There is no need to use smp_mb() and cmpxchg() any more. Signed-off-by: Takuya Yoshikawa <[email protected]> --- arch/x86/kvm/paging_tmpl.h | 7 ++++--- include/linux/kvm_host.h | 2 +- virt/kvm/kvm_main.c | 11 +++++++---- 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index cba218a..b1e6c1b 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -913,7 +913,8 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr, * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't * used by guest then tlbs are not flushed, so guest is allowed to access the * freed pages. - * And we increase kvm->tlbs_dirty to delay tlbs flush in this case. + * We set tlbs_dirty to let the notifier know this change and delay the flush + * until such a case actually happens. */ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { @@ -942,7 +943,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) return -EINVAL; if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { - vcpu->kvm->tlbs_dirty++; + vcpu->kvm->tlbs_dirty = true; continue; } @@ -957,7 +958,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) if (gfn != sp->gfns[i]) { drop_spte(vcpu->kvm, &sp->spt[i]); - vcpu->kvm->tlbs_dirty++; + vcpu->kvm->tlbs_dirty = true; continue; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index f5937b8..ed1cc89 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -401,7 +401,7 @@ struct kvm { unsigned long mmu_notifier_seq; long mmu_notifier_count; #endif - long tlbs_dirty; + bool tlbs_dirty; struct list_head devices; }; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a9e999a..51744da 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -186,12 +186,15 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) void kvm_flush_remote_tlbs(struct kvm *kvm) { - long dirty_count = kvm->tlbs_dirty; - - smp_mb(); if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH)) ++kvm->stat.remote_tlb_flush; - cmpxchg(&kvm->tlbs_dirty, dirty_count, 0); + /* + * tlbs_dirty is used only for optimizing x86's shadow paging code with + * mmu notifiers in mind, see the note on sync_page(). Since it is + * always protected with mmu_lock there, should kvm_flush_remote_tlbs() + * be called before releasing mmu_lock, this is safe. + */ + kvm->tlbs_dirty = false; } EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
