Revert "KVM: MMU: drop kvm_mmu_zap_mmio_sptes"

Revert back to a dedicated (and slower) mechanism for handling the
scenario where all MMIO shadow PTEs need to be zapped due to overflowing
the MMIO generation number.  The MMIO generation scenario is almost
literally a one-in-a-million occurrence, i.e. is not a performance
sensitive scenario.

Restoring kvm_mmu_zap_mmio_sptes() leaves VM teardown as the only user
of kvm_mmu_invalidate_zap_all_pages() and paves the way for removing
the fast invalidate mechanism altogether.

This reverts commit a8eca9dcc656a405a28ffba43f3d86a1ff0eb331.

Cc: Xiao Guangrong <guangrong.xiao@gmail.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 69daa57b08a7402ee002be47f0be0c98fd425829..aeca3fb1cf63e71a39538c854f9c2b64d398bb80 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -319,6 +319,7 @@ struct kvm_mmu_page {
        struct list_head link;
        struct hlist_node hash_link;
        bool unsync;
+       bool mmio_cached;
 
        /*
         * The following two entries are used to key the shadow page in the

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b81e2cad0237a217fcdb4661cebb3161e6c6a3dd..d80c1558b23cb90a015ba3466a40a4f926d647ae 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -391,6 +391,8 @@ static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
        mask |= (gpa & shadow_nonpresent_or_rsvd_mask)
                << shadow_nonpresent_or_rsvd_mask_len;
 
+       page_header(__pa(sptep))->mmio_cached = true;
+
        trace_mark_mmio_spte(sptep, gfn, access, gen);
        mmu_spte_set(sptep, mask);
 }
@@ -5942,6 +5944,24 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
        return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
 }
 
+static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
+{
+       struct kvm_mmu_page *sp, *node;
+       LIST_HEAD(invalid_list);
+
+       spin_lock(&kvm->mmu_lock);
+restart:
+       list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
+               if (!sp->mmio_cached)
+                       continue;
+               if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
+                       goto restart;
+       }
+
+       kvm_mmu_commit_zap_page(kvm, &invalid_list);
+       spin_unlock(&kvm->mmu_lock);
+}
+
 void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
 {
        WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
@@ -5963,7 +5983,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
         */
        if (unlikely(gen == 0)) {
                kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
-               kvm_mmu_invalidate_zap_all_pages(kvm);
+               kvm_mmu_zap_mmio_sptes(kvm);
        }
 }