On Thu, 2022-05-05 at 11:07 +0700, Suravee Suthikulpanit wrote:
> Maxim,
>
> On 5/4/22 7:12 PM, Maxim Levitsky wrote:
> > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> > > index a8f514212b87..fc3ba6071482 100644
> > > --- a/arch/x86/kvm/svm/avic.c
> > > +++ b/arch/x86/kvm/svm/avic.c
> > > @@ -40,6 +40,15 @@
> > > #define AVIC_GATAG_TO_VMID(x) ((x >> AVIC_VCPU_ID_BITS) & AVIC_VM_ID_MASK)
> > > #define AVIC_GATAG_TO_VCPUID(x) (x & AVIC_VCPU_ID_MASK)
> > >
> > > +enum avic_modes {
> > > + AVIC_MODE_NONE = 0,
> > > + AVIC_MODE_X1,
> > > + AVIC_MODE_X2,
> > > +};
> > > +
> > > +static bool force_avic;
> > > +module_param_unsafe(force_avic, bool, 0444);
> > > +
> > > /* Note:
> > > * This hash table is used to map VM_ID to a struct kvm_svm,
> > > * when handling AMD IOMMU GALOG notification to schedule in
> > > @@ -50,6 +59,7 @@ static DEFINE_HASHTABLE(svm_vm_data_hash, SVM_VM_DATA_HASH_BITS);
> > > static u32 next_vm_id = 0;
> > > static bool next_vm_id_wrapped = 0;
> > > static DEFINE_SPINLOCK(svm_vm_data_hash_lock);
> > > +static enum avic_modes avic_mode;
> > >
> > > /*
> > > * This is a wrapper of struct amd_iommu_ir_data.
> > > @@ -1077,3 +1087,33 @@ void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
> > >
> > > avic_vcpu_load(vcpu);
> > > }
> > > +
> > > +/*
> > > + * Note:
> > > + * - The module param avic enable both xAPIC and x2APIC mode.
> > > + * - Hypervisor can support both xAVIC and x2AVIC in the same guest.
> > > + * - The mode can be switched at run-time.
> > > + */
> > > +bool avic_hardware_setup(struct kvm_x86_ops *x86_ops)
> > > +{
> > > + if (!npt_enabled)
> > > + return false;
> > > +
> > > + if (boot_cpu_has(X86_FEATURE_AVIC)) {
> > > + avic_mode = AVIC_MODE_X1;
> > > + pr_info("AVIC enabled\n");
> > > + } else if (force_avic) {
> > > + pr_warn("AVIC is not supported in CPUID but force enabled");
> > > + pr_warn("Your system might crash and burn");
> > I think in this case avic_mode should also be set to AVIC_MODE_X1
> > (Hopefully this won't be needed for systems that have x2avic enabled)
>
> You are right. My appology :(
>
> Actually, x2AVIC depends on both CPUID bits (i.e. X86_FEATURE_AVIC and X86_FEATURE_X2AVIC).
> If the force_avic option is only applicable to only the X86_FEATURE_AVIC bit, we would
> need to check for the following condition before enabling x2AVIC support in the driver:
>
> if ((X86_FEATURE_AVIC | avic_force) & X86_FEATURE_X2AVIC)
> avic_mode = AVIC_MODE_X2
Let it be just for AVIC_MODE_X1, that is
else if (force_avic) {
pr_warn("AVIC is not supported in CPUID but force enabled");
pr_warn("Your system might crash and burn");
avic_mode = AVIC_MODE_X1;
Best regards,
Maxim Levitsky
>
> Regards,
> Suravee
>
>
