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From: Sean Christopherson <seanjc@google.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Lai Jiangshan <laijs@linux.alibaba.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	kvm@vger.kernel.org
Subject: Re: [PATCH 3/7] KVM: X86: Zap the invalid list after remote tlb flushing
Date: Thu, 2 Sep 2021 21:54:30 +0000	[thread overview]
Message-ID: <YTFIFlU9wtVHf4xd@google.com> (raw)
In-Reply-To: <20210824075524.3354-4-jiangshanlai@gmail.com>

On Tue, Aug 24, 2021, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
> 
> In mmu_sync_children(), it can zap the invalid list after remote tlb flushing.
> Emptifying the invalid list ASAP might help reduce a remote tlb flushing
> in some cases.
> 
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 987953a901d2..a165eb8713bc 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2050,7 +2050,7 @@ static bool mmu_sync_children(struct kvm_vcpu *vcpu,
>  			protected |= rmap_write_protect(vcpu, sp->gfn);
>  
>  		if (protected) {
> -			kvm_flush_remote_tlbs(vcpu->kvm);
> +			kvm_mmu_flush_or_zap(vcpu, &invalid_list, true, flush);

This can just be 

			kvm_mmu_remote_flush_or_zap(vcpu, &invalid_list, true);

since a remote flush always does a local flush too.

Related to the tlbs_dirty revert, to avoid overzealous flushing, kvm_sync_page()
can pass back a "remote_flush" flag instead of doing the flush itself.  Something
like the below, or maybe multiplex an 'int' return.

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index ac260e01e9d8..f61de53de55a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2041,7 +2041,7 @@ static bool mmu_sync_children(struct kvm_vcpu *vcpu,
        struct mmu_page_path parents;
        struct kvm_mmu_pages pages;
        LIST_HEAD(invalid_list);
-       bool flush = false;
+       bool flush = false, remote_flush = false;

        while (mmu_unsync_walk(parent, &pages)) {
                bool protected = false;
@@ -2050,17 +2050,17 @@ static bool mmu_sync_children(struct kvm_vcpu *vcpu,
                        protected |= rmap_write_protect(vcpu, sp->gfn);

                if (protected) {
-                       kvm_mmu_flush_or_zap(vcpu, &invalid_list, true, flush);
-                       flush = false;
+                       kvm_mmu_remote_flush_or_zap(vcpu, &invalid_list, true);
+                       remote_flush = flush = false;
                }

                for_each_sp(pages, sp, parents, i) {
                        kvm_unlink_unsync_page(vcpu->kvm, sp);
-                       flush |= kvm_sync_page(vcpu, sp, &invalid_list);
+                       flush |= kvm_sync_page(vcpu, sp, &invalid_list, &remote_flush);
                        mmu_pages_clear_parents(&parents);
                }
                if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {
-                       kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
+                       kvm_mmu_flush_or_zap(vcpu, &invalid_list, remote_flush, flush);
                        cond_resched_rwlock_write(&vcpu->kvm->mmu_lock);
                        /*
                         * If @parent is not root, the caller doesn't have
@@ -2074,7 +2074,7 @@ static bool mmu_sync_children(struct kvm_vcpu *vcpu,
                }
        }

-       kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
+       kvm_mmu_flush_or_zap(vcpu, &invalid_list, remote_flush, flush);
        return true;
 }

>  			flush = false;
>  		}
>  
> -- 
> 2.19.1.6.gb485710b
> 

  reply	other threads:[~2021-09-02 21:54 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24  7:55 [PATCH 0/7] KVM: X86: MMU: misc fixes and cleanups Lai Jiangshan
2021-08-24  7:55 ` [PATCH 1/7] KVM: X86: Fix missed remote tlb flush in rmap_write_protect() Lai Jiangshan
2021-09-02 21:38   ` Sean Christopherson
2021-09-13  9:57   ` Maxim Levitsky
2021-08-24  7:55 ` [PATCH 2/7] KVM: X86: Synchronize the shadow pagetable before link it Lai Jiangshan
2021-09-02 23:40   ` Sean Christopherson
2021-09-02 23:54     ` Sean Christopherson
2021-09-03  0:44       ` Lai Jiangshan
2021-09-03 16:06         ` Sean Christopherson
2021-09-03 16:25           ` Lai Jiangshan
2021-09-03 16:40             ` Sean Christopherson
2021-09-03 17:00               ` Lai Jiangshan
2021-09-03 16:33           ` Lai Jiangshan
2021-09-03  0:51     ` Lai Jiangshan
2021-09-13 11:30     ` Maxim Levitsky
2021-09-13 20:49       ` Sean Christopherson
2021-09-13 22:31         ` Maxim Levitsky
2021-08-24  7:55 ` [PATCH 3/7] KVM: X86: Zap the invalid list after remote tlb flushing Lai Jiangshan
2021-09-02 21:54   ` Sean Christopherson [this message]
2021-08-24  7:55 ` [PATCH 4/7] KVM: X86: Remove FNAME(update_pte) Lai Jiangshan
2021-09-13  9:49   ` Maxim Levitsky
2021-08-24  7:55 ` [PATCH 5/7] KVM: X86: Don't unsync pagetables when speculative Lai Jiangshan
2021-09-13 11:02   ` Maxim Levitsky
2021-09-18  3:06     ` Lai Jiangshan
2021-08-24  7:55 ` [PATCH 6/7] KVM: X86: Don't check unsync if the original spte is writible Lai Jiangshan
2021-08-24  7:55 ` [PATCH 7/7] KVM: X86: Also prefetch the last range in __direct_pte_prefetch() Lai Jiangshan
2021-08-25 15:18   ` Sean Christopherson
2021-08-25 22:58     ` Lai Jiangshan
2021-08-31 18:02 ` [PATCH 0/7] KVM: X86: MMU: misc fixes and cleanups Lai Jiangshan
2021-08-31 21:57   ` Sean Christopherson

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