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Fri, 08 Oct 2021 19:13:31 -0700 (PDT) Date: Fri, 8 Oct 2021 19:12:13 -0700 In-Reply-To: <20211009021236.4122790-1-seanjc@google.com> Message-Id: <20211009021236.4122790-21-seanjc@google.com> Mime-Version: 1.0 References: <20211009021236.4122790-1-seanjc@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v2 20/43] KVM: VMX: Skip Posted Interrupt updates if APICv is hard disabled From: Sean Christopherson To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211008_191332_775910_97F3DEC3 X-CRM114-Status: GOOD ( 14.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Explicitly skip posted interrupt updates if APICv is disabled in all of KVM, or if the guest doesn't have an in-kernel APIC. The PI descriptor is kept up-to-date if APICv is inhibited, e.g. so that re-enabling APICv doesn't require a bunch of updates, but neither the module param nor the APIC type can be changed on-the-fly. Signed-off-by: Sean Christopherson Reviewed-by: Maxim Levitsky --- arch/x86/kvm/vmx/posted_intr.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 3263056784f5..351666c41bbc 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -28,11 +28,14 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) unsigned int dest; /* - * In case of hot-plug or hot-unplug, we may have to undo - * vmx_vcpu_pi_put even if there is no assigned device. And we - * always keep PI.NDST up to date for simplicity: it makes the - * code easier, and CPU migration is not a fast path. + * To simplify hot-plug and dynamic toggling of APICv, keep PI.NDST and + * PI.SN up-to-date even if there is no assigned device or if APICv is + * deactivated due to a dynamic inhibit bit, e.g. for Hyper-V's SyncIC. */ + if (!enable_apicv || !lapic_in_kernel(vcpu)) + return; + + /* Nothing to do if PI.SN==0 and the vCPU isn't being migrated. */ if (!pi_test_sn(pi_desc) && vcpu->cpu == cpu) return;