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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id y22sm5566150edc.76.2021.10.15.09.02.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Oct 2021 09:02:12 -0700 (PDT) Message-ID: Date: Fri, 15 Oct 2021 18:02:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH 0/2] KVM: X86: Don't reset mmu context when changing PGE or PCID Content-Language: en-US To: Lai Jiangshan , Lai Jiangshan , linux-kernel@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , kvm@vger.kernel.org References: <20210919024246.89230-1-jiangshanlai@gmail.com> <506c12c4-4a56-bcbf-a566-a3e75c0814aa@linux.alibaba.com> From: Paolo Bonzini In-Reply-To: <506c12c4-4a56-bcbf-a566-a3e75c0814aa@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/10/21 18:03, Lai Jiangshan wrote: > Ping > > On 2021/9/19 10:42, Lai Jiangshan wrote: >> From: Lai Jiangshan >> >> This patchset uses kvm_vcpu_flush_tlb_guest() instead of >> kvm_mmu_reset_context() >> when X86_CR4_PGE is changed or X86_CR4_PCIDE is changed 1->0. >> >> Neither X86_CR4_PGE nor X86_CR4_PCIDE participates in kvm_mmu_role, so >> kvm_mmu_reset_context() is not required to be invoked.  Only flushing tlb >> is required as SDM says. >> >> The patchset has nothing to do with performance, because the overheads of >> kvm_mmu_reset_context() and kvm_vcpu_flush_tlb_guest() are the same.  And >> even in the [near] future, kvm_vcpu_flush_tlb_guest() will be optimized, >> the code is not in the hot path. >> >> This patchset makes the code more clear when to reset the mmu context. >> And it makes KVM_MMU_CR4_ROLE_BITS consistent with kvm_mmu_role. >> >> Lai Jiangshan (2): >>    KVM: X86: Don't reset mmu context when X86_CR4_PCIDE 1->0 >>    KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE >> >>   arch/x86/kvm/mmu.h | 5 ++--- >>   arch/x86/kvm/x86.c | 7 +++++-- >>   2 files changed, 7 insertions(+), 5 deletions(-) >> > Queued with kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu) replacement, thanks. Paolo