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SubjectRe: [PATCH] KVM/MMU: Combine flushing remote tlb in mmu_set_spte()
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Hi Junaid:
Thanks for your review.

On 7/25/2018 10:26 AM, Junaid Shahid wrote:
> On 07/24/2018 07:35 AM, Paolo Bonzini wrote:
>> On 24/07/2018 10:17, Tianyu Lan wrote:
>>> 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>
>>
>> Looks good, but I'd like a second opinion. Guangrong, Junaid, can you
>> review this?
>>
>> Thanks,
>>
>> Paolo
>>
>>> ---
>>> 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)))
>>>
>>
>
> Reviewed-by: Junaid Shahid <junaids@google.com>
>
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