KVM: MMU: fold tlb flush judgement into mmu_spte_update

mmu_spte_update() is the common function, we can easily audit the path

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 20 insertions, 13 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ed9e96806082..a2fc65ba76a5 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -479,15 +479,24 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte)
 
 /* Rules for using mmu_spte_update:
  * Update the state bits, it means the mapped pfn is not changged.
+ *
+ * Whenever we overwrite a writable spte with a read-only one we
+ * should flush remote TLBs. Otherwise rmap_write_protect
+ * will find a read-only spte, even though the writable spte
+ * might be cached on a CPU's TLB, the return value indicates this
+ * case.
  */
-static void mmu_spte_update(u64 *sptep, u64 new_spte)
+static bool mmu_spte_update(u64 *sptep, u64 new_spte)
 {
         u64 mask, old_spte = *sptep;
+        bool ret = false;
 
         WARN_ON(!is_rmap_spte(new_spte));
 
-        if (!is_shadow_present_pte(old_spte))
-                return mmu_spte_set(sptep, new_spte);
+        if (!is_shadow_present_pte(old_spte)) {
+                mmu_spte_set(sptep, new_spte);
+                return ret;
+        }
 
         new_spte |= old_spte & shadow_dirty_mask;
 
@@ -500,13 +509,18 @@ static void mmu_spte_update(u64 *sptep, u64 new_spte)
         else
                 old_spte = __update_clear_spte_slow(sptep, new_spte);
 
+        if (is_writable_pte(old_spte) && !is_writable_pte(new_spte))
+                ret = true;
+
         if (!shadow_accessed_mask)
-                return;
+                return ret;
 
         if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
                 kvm_set_pfn_accessed(spte_to_pfn(old_spte));
         if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
                 kvm_set_pfn_dirty(spte_to_pfn(old_spte));
+
+        return ret;
 }
 
 /*
@@ -2268,7 +2282,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                     gfn_t gfn, pfn_t pfn, bool speculative,
                     bool can_unsync, bool host_writable)
 {
-        u64 spte, entry = *sptep;
+        u64 spte;
         int ret = 0;
 
         if (set_mmio_spte(sptep, gfn, pfn, pte_access))
@@ -2346,14 +2360,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                 mark_page_dirty(vcpu->kvm, gfn);
 
 set_pte:
-        mmu_spte_update(sptep, spte);
-        /*
-         * If we overwrite a writable spte with a read-only one we
-         * should flush remote TLBs. Otherwise rmap_write_protect
-         * will find a read-only spte, even though the writable spte
-         * might be cached on a CPU's TLB.
-         */
-        if (is_writable_pte(entry) && !is_writable_pte(*sptep))
+        if (mmu_spte_update(sptep, spte))
                 kvm_flush_remote_tlbs(vcpu->kvm);
 done:
         return ret;