Hi Maxim,
On 2/25/22 3:06 AM, Maxim Levitsky wrote:
On Sun, 2022-02-20 at 20:19 -0600, Suravee Suthikulpanit wrote:
Currently, AVIC is inactive when booting a VM w/ x2APIC support.
With x2AVIC support, the APICV_INHIBIT_REASON_X2APIC can be removed.
The commit title is a bit misleading - the inhibit reason is not removed,
but rather AVIC is not inhibited when x2avic is present.
I'll fix the commit message.
Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@xxxxxxx>
---
arch/x86/kvm/svm/avic.c | 21 +++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 18 ++----------------
arch/x86/kvm/svm/svm.h | 1 +
3 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 3306b74f1d8b..874c89f8fd47 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -21,6 +21,7 @@
#include <asm/irq_remapping.h>
+#include "cpuid.h"
#include "trace.h"
#include "lapic.h"
#include "x86.h"
@@ -176,6 +177,26 @@ void avic_vm_destroy(struct kvm *kvm)
spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);
}
+void avic_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu, int nested)
+{
+ /*
+ * If the X2APIC feature is exposed to the guest,
+ * disable AVIC unless X2AVIC mode is enabled.
+ */
+ if (avic_mode == AVIC_MODE_X1 &&
+ guest_cpuid_has(vcpu, X86_FEATURE_X2APIC))
+ kvm_request_apicv_update(vcpu->kvm, false,
+ APICV_INHIBIT_REASON_X2APIC);
+
+ /*
+ * Currently, AVIC does not work with nested virtualization.
+ * So, we disable AVIC when cpuid for SVM is set in the L1 guest.
+ */
+ if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM))
+ kvm_request_apicv_update(vcpu->kvm, false,
+ APICV_INHIBIT_REASON_NESTED);
BTW, now that I am thinking about it, it would be nice to be able to force
the AVIC_MODE_X1 even if x2avic is present, for debug purposes from a module
param. Just a suggestion.
Actually, we can force AVIC_MODE_X1 on a VM by disabling Guest x2APIC mode via QEMU option.
That should work for debugging purpose, right?
Regards,
Suravee
