KVM: SVM: Don't put/load AVIC when setting virtual APIC mode
authorSean Christopherson <seanjc@google.com>
Fri, 6 Jan 2023 01:12:40 +0000 (01:12 +0000)
committerPaolo Bonzini <pbonzini@redhat.com>
Fri, 13 Jan 2023 15:45:24 +0000 (10:45 -0500)
Move the VMCB updates from avic_refresh_apicv_exec_ctrl() into
avic_set_virtual_apic_mode() and invert the dependency being said
functions to avoid calling avic_vcpu_{load,put}() and
avic_set_pi_irte_mode() when "only" setting the virtual APIC mode.

avic_set_virtual_apic_mode() is invoked from common x86 with preemption
enabled, which makes avic_vcpu_{load,put}() unhappy.  Luckily, calling
those and updating IRTE stuff is unnecessary as the only reason
avic_set_virtual_apic_mode() is called is to handle transitions between
xAPIC and x2APIC that don't also toggle APICv activation.  And if
activation doesn't change, there's no need to fiddle with the physical
APIC ID table or update IRTE.

The "full" refresh is guaranteed to be called if activation changes in
this case as the only call to the "set" path is:

kvm_vcpu_update_apicv(vcpu);
static_call_cond(kvm_x86_set_virtual_apic_mode)(vcpu);

and kvm_vcpu_update_apicv() invokes the refresh if activation changes:

if (apic->apicv_active == activate)
goto out;

apic->apicv_active = activate;
kvm_apic_update_apicv(vcpu);
static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);

Rename the helper to reflect that it is also called during "refresh".

  WARNING: CPU: 183 PID: 49186 at arch/x86/kvm/svm/avic.c:1081 avic_vcpu_put+0xde/0xf0 [kvm_amd]
  CPU: 183 PID: 49186 Comm: stable Tainted: G           O       6.0.0-smp--fcddbca45f0a-sink #34
  Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 10.48.0 01/27/2022
  RIP: 0010:avic_vcpu_put+0xde/0xf0 [kvm_amd]
   avic_refresh_apicv_exec_ctrl+0x142/0x1c0 [kvm_amd]
   avic_set_virtual_apic_mode+0x5a/0x70 [kvm_amd]
   kvm_lapic_set_base+0x149/0x1a0 [kvm]
   kvm_set_apic_base+0x8f/0xd0 [kvm]
   kvm_set_msr_common+0xa3a/0xdc0 [kvm]
   svm_set_msr+0x364/0x6b0 [kvm_amd]
   __kvm_set_msr+0xb8/0x1c0 [kvm]
   kvm_emulate_wrmsr+0x58/0x1d0 [kvm]
   msr_interception+0x1c/0x30 [kvm_amd]
   svm_invoke_exit_handler+0x31/0x100 [kvm_amd]
   svm_handle_exit+0xfc/0x160 [kvm_amd]
   vcpu_enter_guest+0x21bb/0x23e0 [kvm]
   vcpu_run+0x92/0x450 [kvm]
   kvm_arch_vcpu_ioctl_run+0x43e/0x6e0 [kvm]
   kvm_vcpu_ioctl+0x559/0x620 [kvm]

Fixes: 05c4fe8c1bd9 ("KVM: SVM: Refresh AVIC configuration when changing APIC mode")
Cc: stable@vger.kernel.org
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230106011306.85230-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kvm/svm/avic.c
arch/x86/kvm/svm/svm.c
arch/x86/kvm/svm/svm.h

index 3b2c88b168ba344c3edf166806eb3ec2880778fe..97ad0661f96394e9cb38f6ffa9692feb17b0aedf 100644 (file)
@@ -747,18 +747,6 @@ void avic_apicv_post_state_restore(struct kvm_vcpu *vcpu)
        avic_handle_ldr_update(vcpu);
 }
 
-void avic_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
-{
-       if (!lapic_in_kernel(vcpu) || avic_mode == AVIC_MODE_NONE)
-               return;
-
-       if (kvm_get_apic_mode(vcpu) == LAPIC_MODE_INVALID) {
-               WARN_ONCE(true, "Invalid local APIC state (vcpu_id=%d)", vcpu->vcpu_id);
-               return;
-       }
-       avic_refresh_apicv_exec_ctrl(vcpu);
-}
-
 static int avic_set_pi_irte_mode(struct kvm_vcpu *vcpu, bool activate)
 {
        int ret = 0;
@@ -1100,17 +1088,18 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
        WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
 }
 
-
-void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
+void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
        struct vmcb *vmcb = svm->vmcb01.ptr;
-       bool activated = kvm_vcpu_apicv_active(vcpu);
+
+       if (!lapic_in_kernel(vcpu) || avic_mode == AVIC_MODE_NONE)
+               return;
 
        if (!enable_apicv)
                return;
 
-       if (activated) {
+       if (kvm_vcpu_apicv_active(vcpu)) {
                /**
                 * During AVIC temporary deactivation, guest could update
                 * APIC ID, DFR and LDR registers, which would not be trapped
@@ -1124,6 +1113,16 @@ void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
                avic_deactivate_vmcb(svm);
        }
        vmcb_mark_dirty(vmcb, VMCB_AVIC);
+}
+
+void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
+{
+       bool activated = kvm_vcpu_apicv_active(vcpu);
+
+       if (!enable_apicv)
+               return;
+
+       avic_refresh_virtual_apic_mode(vcpu);
 
        if (activated)
                avic_vcpu_load(vcpu, vcpu->cpu);
index 6ffadbd5774472a3da0abbe25dcd0119ed6580be..26044e1d2422c7f528d6f4af1ffe5a8b4b92e9cd 100644 (file)
@@ -4771,7 +4771,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
        .enable_nmi_window = svm_enable_nmi_window,
        .enable_irq_window = svm_enable_irq_window,
        .update_cr8_intercept = svm_update_cr8_intercept,
-       .set_virtual_apic_mode = avic_set_virtual_apic_mode,
+       .set_virtual_apic_mode = avic_refresh_virtual_apic_mode,
        .refresh_apicv_exec_ctrl = avic_refresh_apicv_exec_ctrl,
        .check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons,
        .apicv_post_state_restore = avic_apicv_post_state_restore,
index 4826e6cc611bf1305c55c93c52f2364bf40d4506..d0ed3f59522956f20c8f4835015f44eb164aabb0 100644 (file)
@@ -648,7 +648,7 @@ void avic_vcpu_blocking(struct kvm_vcpu *vcpu);
 void avic_vcpu_unblocking(struct kvm_vcpu *vcpu);
 void avic_ring_doorbell(struct kvm_vcpu *vcpu);
 unsigned long avic_vcpu_get_apicv_inhibit_reasons(struct kvm_vcpu *vcpu);
-void avic_set_virtual_apic_mode(struct kvm_vcpu *vcpu);
+void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu);
 
 
 /* sev.c */