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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id k184sm11767549wme.1.2020.08.31.06.09.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2020 06:09:16 -0700 (PDT) From: Vitaly Kuznetsov To: Lai Jiangshan , LKML , Sean Christopherson Cc: Lai Jiangshan , Paolo Bonzini , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , X86 ML , "H. Peter Anvin" , kvm@vger.kernel.org Subject: Re: [PATCH] kvm x86/mmu: use KVM_REQ_MMU_SYNC to sync when needed In-Reply-To: References: <20200824101825.4106-1-jiangshanlai@gmail.com> Date: Mon, 31 Aug 2020 15:09:15 +0200 Message-ID: <875z8zx8qs.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Lai Jiangshan writes: > Ping @Sean Christopherson > Let's try 'Beetlejuice' instead :-) > On Mon, Aug 24, 2020 at 5:18 PM Lai Jiangshan wrote: >> >> From: Lai Jiangshan >> >> 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) >> changed it without giving any reason in the changelog. >> >> In theory, the syncing is needed, and need to be fixed by reverting >> this part of change. Even if the original commit is not wordy enough this is hardly better. Are you seeing a particular scenario when a change in current vCPU's MMU requires flushing TLB entries for *other* contexts, ... (see below) >> >> Signed-off-by: Lai Jiangshan >> --- >> 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 4e03841f053d..9a93de921f2b 100644 >> --- a/arch/x86/kvm/mmu/mmu.c >> +++ b/arch/x86/kvm/mmu/mmu.c >> @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, >> } >> >> if (sp->unsync_children) >> - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); >> + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); ... in particular, why are you reverting only this hunk? Please elaborate. >> >> __clear_sp_write_flooding_count(sp); >> >> -- >> 2.19.1.6.gb485710b >> > -- Vitaly