[PATCH] KVM: x86: inhibit APICv when KVM_GUESTDBG_BLOCKIRQ active

Maxim Levitsky
2021-11-03T09:29:26Z

KVM_GUESTDBG_BLOCKIRQ relies on interrupts being injected using
standard kvm's inject_pending_event, and not via APICv/AVIC.

Since this is a debug feature, just inhibit it while it
is in use.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm/avic.c | 3 ++-
arch/x86/kvm/vmx/vmx.c | 3 ++-
arch/x86/kvm/x86.c | 3 +++
4 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 88fce6ab4bbd7..8f6e15b95a4d8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1034,6 +1034,7 @@ struct kvm_x86_msr_filter {
#define APICV_INHIBIT_REASON_IRQWIN 3
#define APICV_INHIBIT_REASON_PIT_REINJ 4
#define APICV_INHIBIT_REASON_X2APIC 5
+#define APICV_INHIBIT_REASON_BLOCKIRQ 6

struct kvm_arch {
unsigned long n_used_mmu_pages;
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 8052d92069e01..affc0ea98d302 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -904,7 +904,8 @@ bool svm_check_apicv_inhibit_reasons(ulong bit)
BIT(APICV_INHIBIT_REASON_NESTED) |
BIT(APICV_INHIBIT_REASON_IRQWIN) |
BIT(APICV_INHIBIT_REASON_PIT_REINJ) |
- BIT(APICV_INHIBIT_REASON_X2APIC);
+ BIT(APICV_INHIBIT_REASON_X2APIC) |
+ BIT(APICV_INHIBIT_REASON_BLOCKIRQ);

return supported & BIT(bit);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 71f54d85f104c..e4fc9ff7cd944 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7565,7 +7565,8 @@ static void hardware_unsetup(void)
static bool vmx_check_apicv_inhibit_reasons(ulong bit)
{
ulong supported = BIT(APICV_INHIBIT_REASON_DISABLE) |
- BIT(APICV_INHIBIT_REASON_HYPERV);
+ BIT(APICV_INHIBIT_REASON_HYPERV) |
+ BIT(APICV_INHIBIT_REASON_BLOCKIRQ);

return supported & BIT(bit);
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ac83d873d65b0..eb3b8d2375713 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10747,6 +10747,9 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
vcpu->arch.singlestep_rip = kvm_get_linear_rip(vcpu);

+ kvm_request_apicv_update(vcpu->kvm,
+ !(vcpu->guest_debug & KVM_GUESTDBG_BLOCKIRQ),
+ APICV_INHIBIT_REASON_BLOCKIRQ);
/*
* Trigger an rflags update that will inject or remove the trace
* flags.
--
2.26.3