[PATCH v7 05/10] KVM: MMU: fold tlb flush judgement into mmu_spte_update

[Xiao Guangrong]

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

Signed-off-by: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |   33 ++++++++++++++++++++-------------
 1 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a0ea746..6ebbb7a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -478,15 +478,24 @@ 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;

@@ -499,13 +508,18 @@ 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;
 }

 /*
@@ -2271,7 +2285,7 @@ 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))
@@ -2349,14 +2363,7 @@ 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;
-- 
1.7.7.6

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