[PATCH 6/10] KVM MMU: don't write-protect if have new mapping to unsync page

[Xiao Guangrong]

If have new mapping to the unsync page(i.e, add a new parent), just
update the page from sp->gfn but not write-protect gfn, and if need
create new shadow page form sp->gfn, we should sync it

Signed-off-by: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>
---
 arch/x86/kvm/mmu.c |   27 +++++++++++++++++++--------
 1 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fd027a6..8607a64 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1196,16 +1196,20 @@ static void kvm_unlink_unsync_page(struct kvm *kvm, 
struct kvm_mmu_page *sp)
 
 static int kvm_mmu_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp);
 
-static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
+                        bool clear_unsync)
 {
        if (sp->role.cr4_pae != !!is_pae(vcpu)) {
                kvm_mmu_zap_page(vcpu->kvm, sp);
                return 1;
        }
 
-       if (rmap_write_protect(vcpu->kvm, sp->gfn))
-               kvm_flush_remote_tlbs(vcpu->kvm);
-       kvm_unlink_unsync_page(vcpu->kvm, sp);
+       if (clear_unsync) {
+               if (rmap_write_protect(vcpu->kvm, sp->gfn))
+                       kvm_flush_remote_tlbs(vcpu->kvm);
+               kvm_unlink_unsync_page(vcpu->kvm, sp);
+       }
+
        if (vcpu->arch.mmu.sync_page(vcpu, sp)) {
                kvm_mmu_zap_page(vcpu->kvm, sp);
                return 1;
@@ -1293,7 +1297,7 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
                        kvm_flush_remote_tlbs(vcpu->kvm);
 
                for_each_sp(pages, sp, parents, i) {
-                       kvm_sync_page(vcpu, sp);
+                       kvm_sync_page(vcpu, sp, true);
                        mmu_pages_clear_parents(&parents);
                }
                cond_resched_lock(&vcpu->kvm->mmu_lock);
@@ -1313,7 +1317,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct 
kvm_vcpu *vcpu,
        unsigned index;
        unsigned quadrant;
        struct hlist_head *bucket;
-       struct kvm_mmu_page *sp;
+       struct kvm_mmu_page *sp, *unsync_sp = NULL;
        struct hlist_node *node, *tmp;
 
        role = vcpu->arch.mmu.base_role;
@@ -1332,12 +1336,16 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct 
kvm_vcpu *vcpu,
        hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
                if (sp->gfn == gfn) {
                        if (sp->unsync)
-                               if (kvm_sync_page(vcpu, sp))
-                                       continue;
+                               unsync_sp = sp;
 
                        if (sp->role.word != role.word)
                                continue;
 
+                       if (unsync_sp && kvm_sync_page(vcpu, unsync_sp, false)) 
{
+                               unsync_sp = NULL;
+                               continue;
+                       }
+
                        mmu_page_add_parent_pte(vcpu, sp, parent_pte);
                        if (sp->unsync_children) {
                                set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests);
@@ -1346,6 +1354,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct 
kvm_vcpu *vcpu,
                        trace_kvm_mmu_get_page(sp, false);
                        return sp;
                }
+       if (unsync_sp)
+               kvm_sync_page(vcpu, unsync_sp, true);
+
        ++vcpu->kvm->stat.mmu_cache_miss;
        sp = kvm_mmu_alloc_page(vcpu, parent_pte);
        if (!sp)
-- 
1.6.1.2


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