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KVM: ensure APICv is considered inactive if there is no APIC

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kvm_vcpu_apicv_active() returns false if a virtual machine has no in-kernel
local APIC, however kvm_apicv_activated might still be true if there are
no reasons to disable APICv; in fact it is quite likely that there is none
because APICv is inhibited by specific configurations of the local APIC
and those configurations cannot be programmed.  This triggers a WARN:

   WARN_ON_ONCE(kvm_apicv_activated(vcpu->kvm) != kvm_vcpu_apicv_active(vcpu));

To avoid this, introduce another cause for APICv inhibition, namely the
absence of an in-kernel local APIC.  This cause is enabled by default,
and is dropped by either KVM_CREATE_IRQCHIP or the enabling of
KVM_CAP_IRQCHIP_SPLIT.

Reported-by: Ignat Korchagin <ignat@cloudflare.com>
Fixes: ee49a89329 ("KVM: x86: Move SVM's APICv sanity check to common x86", 2021-10-22)
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Ignat Korchagin <ignat@cloudflare.com>
Message-Id: <20211130123746.293379-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
2021-11-30 07:37:45 -05:00
parent cb1d220da0
commit ef8b4b7203
4 changed files with 8 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/kvm_host.h
View File

@@ -1036,6 +1036,7 @@ struct kvm_x86_msr_filter {
#define APICV_INHIBIT_REASON_PIT_REINJ 4 #define APICV_INHIBIT_REASON_PIT_REINJ 4
#define APICV_INHIBIT_REASON_X2APIC 5 #define APICV_INHIBIT_REASON_X2APIC 5
#define APICV_INHIBIT_REASON_BLOCKIRQ 6 #define APICV_INHIBIT_REASON_BLOCKIRQ 6
#define APICV_INHIBIT_REASON_ABSENT 7
struct kvm_arch { struct kvm_arch {
unsigned long n_used_mmu_pages; unsigned long n_used_mmu_pages;

1
arch/x86/kvm/svm/avic.c
View File

@@ -900,6 +900,7 @@ out:
bool svm_check_apicv_inhibit_reasons(ulong bit) bool svm_check_apicv_inhibit_reasons(ulong bit)
{ {
ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) | ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) |
BIT(APICV_INHIBIT_REASON_ABSENT) |
BIT(APICV_INHIBIT_REASON_HYPERV) | BIT(APICV_INHIBIT_REASON_HYPERV) |
BIT(APICV_INHIBIT_REASON_NESTED) | BIT(APICV_INHIBIT_REASON_NESTED) |
BIT(APICV_INHIBIT_REASON_IRQWIN) | BIT(APICV_INHIBIT_REASON_IRQWIN) |

1
arch/x86/kvm/vmx/vmx.c
View File

@@ -7525,6 +7525,7 @@ static void hardware_unsetup(void)
static bool vmx_check_apicv_inhibit_reasons(ulong bit) static bool vmx_check_apicv_inhibit_reasons(ulong bit)
{ {
ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) | ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) |
BIT(APICV_INHIBIT_REASON_ABSENT) |
BIT(APICV_INHIBIT_REASON_HYPERV) | BIT(APICV_INHIBIT_REASON_HYPERV) |
BIT(APICV_INHIBIT_REASON_BLOCKIRQ); BIT(APICV_INHIBIT_REASON_BLOCKIRQ);

7
arch/x86/kvm/x86.c
View File

@@ -5740,6 +5740,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
smp_wmb(); smp_wmb();
kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT; kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT;
kvm->arch.nr_reserved_ioapic_pins = cap->args[0]; kvm->arch.nr_reserved_ioapic_pins = cap->args[0];
kvm_request_apicv_update(kvm, true, APICV_INHIBIT_REASON_ABSENT);
r = 0; r = 0;
split_irqchip_unlock: split_irqchip_unlock:
mutex_unlock(&kvm->lock); mutex_unlock(&kvm->lock);
@@ -6120,6 +6121,7 @@ set_identity_unlock:
/* Write kvm->irq_routing before enabling irqchip_in_kernel. */ /* Write kvm->irq_routing before enabling irqchip_in_kernel. */
smp_wmb(); smp_wmb();
kvm->arch.irqchip_mode = KVM_IRQCHIP_KERNEL; kvm->arch.irqchip_mode = KVM_IRQCHIP_KERNEL;
kvm_request_apicv_update(kvm, true, APICV_INHIBIT_REASON_ABSENT);
create_irqchip_unlock: create_irqchip_unlock:
mutex_unlock(&kvm->lock); mutex_unlock(&kvm->lock);
break; break;
@@ -8818,10 +8820,9 @@ static void kvm_apicv_init(struct kvm *kvm)
{ {
init_rwsem(&kvm->arch.apicv_update_lock); init_rwsem(&kvm->arch.apicv_update_lock);
if (enable_apicv) set_bit(APICV_INHIBIT_REASON_ABSENT,
clear_bit(APICV_INHIBIT_REASON_DISABLE,
&kvm->arch.apicv_inhibit_reasons); &kvm->arch.apicv_inhibit_reasons);
else if (!enable_apicv)
set_bit(APICV_INHIBIT_REASON_DISABLE, set_bit(APICV_INHIBIT_REASON_DISABLE,
&kvm->arch.apicv_inhibit_reasons); &kvm->arch.apicv_inhibit_reasons);
} }