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Subject[PATCH] KVM/MMU: Combine flushing remote tlb in mmu_set_spte()
Date
mmu_set_spte() flushes remote tlbs for drop_parent_pte/drop_spte()
and set_spte() separately. This may introduce redundant flush. This
patch is to combine these flushes and check flush request after
calling set_spte().

Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
---
arch/x86/kvm/mmu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 22a7984..8f21632 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2901,6 +2901,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
int rmap_count;
int set_spte_ret;
int ret = RET_PF_RETRY;
+ bool flush = false;

pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
*sptep, write_fault, gfn);
@@ -2917,12 +2918,12 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,

child = page_header(pte & PT64_BASE_ADDR_MASK);
drop_parent_pte(child, sptep);
- kvm_flush_remote_tlbs(vcpu->kvm);
+ flush = true;
} else if (pfn != spte_to_pfn(*sptep)) {
pgprintk("hfn old %llx new %llx\n",
spte_to_pfn(*sptep), pfn);
drop_spte(vcpu->kvm, sptep);
- kvm_flush_remote_tlbs(vcpu->kvm);
+ flush = true;
} else
was_rmapped = 1;
}
@@ -2934,7 +2935,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
ret = RET_PF_EMULATE;
kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
}
- if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)
+ if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH || flush)
kvm_flush_remote_tlbs(vcpu->kvm);

if (unlikely(is_mmio_spte(*sptep)))
--
2.7.4
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