• Sean Christopherson's avatar
    KVM: SVM: Don't put/load AVIC when setting virtual APIC mode · e0bead97
    Sean Christopherson authored
    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: 05c4fe8c ("KVM: SVM: Refresh AVIC configuration when changing APIC mode")
    Cc: stable@vger.kernel.org
    Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
    Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
    Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
    Message-Id: <20230106011306.85230-8-seanjc@google.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    e0bead97
svm.h 18.9 KB