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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id i14-20020a17090332ce00b00189422a6b8bsm5800996plr.91.2022.12.02.07.49.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Dec 2022 07:49:30 -0800 (PST) Date: Fri, 2 Dec 2022 15:49:27 +0000 From: Sean Christopherson To: Yuan ZhaoXiong Cc: pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mlevitsk@redhat.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: fix APICv/x2AVIC disabled when vm reboot by itself Message-ID: References: <1669984574-32692-1-git-send-email-yuanzhaoxiong@baidu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1669984574-32692-1-git-send-email-yuanzhaoxiong@baidu.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2022, Yuan ZhaoXiong wrote: > This patch fixes that VM rebooting itself will cause APICv > disabled when VM is started with APICv/x2AVIC enabled. > > When a VM reboot itself, The Qemu whill reset LAPIC by invoking > ioctl(KVM_SET_LAPIC, ...) to disable x2APIC mode and set APIC_ID > to its vcpuid in xAPIC mode. > > That will be handled in KVM as follows: > > kvm_vcpu_ioctl_set_lapic > kvm_apic_set_state > kvm_lapic_set_base => disable X2APIC mode > kvm_apic_state_fixup > kvm_lapic_xapic_id_updated > kvm_xapic_id(apic) != apic->vcpu->vcpu_id > kvm_set_apicv_inhibit(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) > memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s)) => update APIC_ID > > kvm_apic_set_state invokes kvm_lapic_set_base to disable x2APIC mode > firstly, but don't change APIC_ID, APIC_ID is 32 bits in x2APIC mode > and 8 bist(bit 24 ~ bit 31) in xAPIC mode. So kvm_lapic_xapic_id_updated > will set APICV_INHIBIT_REASON_APIC_ID_MODIFIED bit inhibit and disable > APICv/x2AVIC. > > kvm_lapic_xapic_id_updated must be called after APIC_ID is changed. > > Fixes: 3743c2f02517 ("KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base") > > Signed-off-by: Yuan ZhaoXiong > --- > arch/x86/kvm/lapic.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index d7639d1..bf5ce86 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -2722,8 +2722,6 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu, > icr = __kvm_lapic_get_reg64(s->regs, APIC_ICR); > __kvm_lapic_set_reg(s->regs, APIC_ICR2, icr >> 32); > } > - } else { > - kvm_lapic_xapic_id_updated(vcpu->arch.apic); > } > > return 0; > @@ -2759,6 +2757,9 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s) > } > memcpy(vcpu->arch.apic->regs, s->regs, sizeof(*s)); > > + if (!apic_x2apic_mode(apic)) > + kvm_lapic_xapic_id_updated(apic); > + Already posted[*], along with a pile of other APIC fixes. Hopefully it will land in 6.2. [*] https://lore.kernel.org/all/20221001005915.2041642-7-seanjc@google.com