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[149.6.153.186]) by smtp.googlemail.com with ESMTPSA id n65-20020a1c2744000000b003862bfb509bsm9776282wmn.46.2022.04.08.03.10.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Apr 2022 03:10:34 -0700 (PDT) Message-ID: Date: Fri, 8 Apr 2022 12:10:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH] KVM: x86/mmu: remove unnecessary kvm_shadow_root_allocated() check Content-Language: en-US To: luofei , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org Cc: seanjc@google.com, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220407014016.1266469-1-luofei@unicloud.com> From: Paolo Bonzini In-Reply-To: <20220407014016.1266469-1-luofei@unicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-5.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A, RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/7/22 03:40, luofei wrote: > When we reach here, the return value of kvm_shadow_root_allocated() > has already been checked to false under kvm->slots_arch_lock. > So remove the unnecessary recheck. It's a little less clear t check !is_tdp_mmu_enabled(). That said, this is only done once, so perhaps it's better/easier to just remove the if completely. Paolo > Signed-off-by: luofei > --- > 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 8f19ea752704..1978ee527298 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3394,7 +3394,7 @@ static int mmu_first_shadow_root_alloc(struct kvm *kvm) > * Check if anything actually needs to be allocated, e.g. all metadata > * will be allocated upfront if TDP is disabled. > */ > - if (kvm_memslots_have_rmaps(kvm) && > + if (!is_tdp_mmu_enabled(kvm) && > kvm_page_track_write_tracking_enabled(kvm)) > goto out_success; >