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    SubjectRe: [PATCH v4 03/15] KVM: SVM: Detect X2APIC virtualization (x2AVIC) support
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    On Sat, 2022-05-07 at 21:39 -0500, Suravee Suthikulpanit wrote:
    > Add CPUID check for the x2APIC virtualization (x2AVIC) feature.
    > If available, the SVM driver can support both AVIC and x2AVIC modes
    > when load the kvm_amd driver with avic=1. The operating mode will be
    > determined at runtime depending on the guest APIC mode.
    >
    > Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
    > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
    > ---
    > arch/x86/include/asm/svm.h | 3 +++
    > arch/x86/kvm/svm/avic.c | 51 ++++++++++++++++++++++++++++++++++++++
    > arch/x86/kvm/svm/svm.c | 15 ++---------
    > arch/x86/kvm/svm/svm.h | 1 +
    > 4 files changed, 57 insertions(+), 13 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
    > index f70a5108d464..2c2a104b777e 100644
    > --- a/arch/x86/include/asm/svm.h
    > +++ b/arch/x86/include/asm/svm.h
    > @@ -195,6 +195,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
    > #define AVIC_ENABLE_SHIFT 31
    > #define AVIC_ENABLE_MASK (1 << AVIC_ENABLE_SHIFT)
    >
    > +#define X2APIC_MODE_SHIFT 30
    > +#define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
    > +
    > #define LBR_CTL_ENABLE_MASK BIT_ULL(0)
    > #define VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK BIT_ULL(1)
    >
    > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
    > index a8f514212b87..95006bbdf970 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 +1087,44 @@ 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) {
    > + /*
    > + * Some older systems does not advertise AVIC support.
    > + * See Revision Guide for specific AMD processor for more detail.
    > + */
    > + avic_mode = AVIC_MODE_X1;
    > + pr_warn("AVIC is not supported in CPUID but force enabled");
    > + pr_warn("Your system might crash and burn");
    > + }
    > +
    > + /* AVIC is a prerequisite for x2AVIC. */
    > + if (boot_cpu_has(X86_FEATURE_X2AVIC)) {
    > + if (avic_mode == AVIC_MODE_X1) {
    > + avic_mode = AVIC_MODE_X2;
    > + pr_info("x2AVIC enabled\n");
    > + } else {
    > + pr_warn(FW_BUG "Cannot support x2AVIC due to AVIC is disabled");
    > + pr_warn(FW_BUG "Try enable AVIC using force_avic option");
    > + }
    > + }
    > +
    > + if (avic_mode != AVIC_MODE_NONE)
    > + amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
    > +
    > + return !!avic_mode;
    > +}
    > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
    > index 3b49337998ec..74e6f86f5dc3 100644
    > --- a/arch/x86/kvm/svm/svm.c
    > +++ b/arch/x86/kvm/svm/svm.c
    > @@ -188,9 +188,6 @@ module_param(tsc_scaling, int, 0444);
    > static bool avic;
    > module_param(avic, bool, 0444);
    >
    > -static bool force_avic;
    > -module_param_unsafe(force_avic, bool, 0444);
    > -
    > bool __read_mostly dump_invalid_vmcb;
    > module_param(dump_invalid_vmcb, bool, 0644);
    >
    > @@ -4913,17 +4910,9 @@ static __init int svm_hardware_setup(void)
    > nrips = false;
    > }
    >
    > - enable_apicv = avic = avic && npt_enabled && (boot_cpu_has(X86_FEATURE_AVIC) || force_avic);
    > + enable_apicv = avic = avic && avic_hardware_setup(&svm_x86_ops);
    >
    > - if (enable_apicv) {
    > - if (!boot_cpu_has(X86_FEATURE_AVIC)) {
    > - pr_warn("AVIC is not supported in CPUID but force enabled");
    > - pr_warn("Your system might crash and burn");
    > - } else
    > - pr_info("AVIC enabled\n");
    > -
    > - amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
    > - } else {
    > + if (!enable_apicv) {
    > svm_x86_ops.vcpu_blocking = NULL;
    > svm_x86_ops.vcpu_unblocking = NULL;
    > svm_x86_ops.vcpu_get_apicv_inhibit_reasons = NULL;
    > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
    > index 32220a1b0ea2..678fc7757fe4 100644
    > --- a/arch/x86/kvm/svm/svm.h
    > +++ b/arch/x86/kvm/svm/svm.h
    > @@ -603,6 +603,7 @@ extern struct kvm_x86_nested_ops svm_nested_ops;
    >
    > /* avic.c */
    >
    > +bool avic_hardware_setup(struct kvm_x86_ops *ops);
    > int avic_ga_log_notifier(u32 ga_tag);
    > void avic_vm_destroy(struct kvm *kvm);
    > int avic_vm_init(struct kvm *kvm);

    Looks great!

    Best regars,
    Maxim Levitsky

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