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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id 137sm5080242pfx.172.2021.04.23.08.18.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Apr 2021 08:18:25 -0700 (PDT) Date: Fri, 23 Apr 2021 15:18:22 +0000 From: Sean Christopherson To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: [PATCH v2] KVM: x86/xen: Take srcu lock when accessing kvm_memslots() Message-ID: References: <1619166200-9215-1-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1619166200-9215-1-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Apr 23, 2021, Wanpeng Li wrote: > From: Wanpeng Li > > kvm_memslots() will be called by kvm_write_guest_offset_cached() so we should > take the srcu lock. Let's pull the srcu lock operation from kvm_steal_time_set_preempted() > again to fix xen part. > > Fixes: 30b5c851af7 (KVM: x86/xen: Add support for vCPU runstate information) > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/x86.c | 20 +++++++++----------- > 1 file changed, 9 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 3bf52ba..c775d24 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4097,7 +4097,6 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) > { > struct kvm_host_map map; > struct kvm_steal_time *st; > - int idx; > > if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) > return; > @@ -4105,15 +4104,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) > if (vcpu->arch.st.preempted) > return; > > - /* > - * Take the srcu lock as memslots will be accessed to check the gfn > - * cache generation against the memslots generation. > - */ > - idx = srcu_read_lock(&vcpu->kvm->srcu); > - > if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map, > &vcpu->arch.st.cache, true)) > - goto out; > + return; > > st = map.hva + > offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS); > @@ -4121,20 +4114,25 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) > st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED; > > kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true); > - > -out: > - srcu_read_unlock(&vcpu->kvm->srcu, idx); > } > > void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > { > + int idx; > + > if (vcpu->preempted && !vcpu->arch.guest_state_protected) > vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu); > > + /* > + * Take the srcu lock as memslots will be accessed to check the gfn > + * cache generation against the memslots generation. > + */ > + idx = srcu_read_lock(&vcpu->kvm->srcu); Might be worth grabbing "kvm" in a local variable? Either way: Reviewed-by: Sean Christopherson > if (kvm_xen_msr_enabled(vcpu->kvm)) > kvm_xen_runstate_set_preempted(vcpu); > else > kvm_steal_time_set_preempted(vcpu); > + srcu_read_unlock(&vcpu->kvm->srcu, idx); > > static_call(kvm_x86_vcpu_put)(vcpu); > vcpu->arch.last_host_tsc = rdtsc(); > -- > 2.7.4 >