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Date: Mon, 09 May 2022 13:15:20 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: pbonzini@...hat.com, seanjc@...gle.com, joro@...tes.org,
jon.grimm@....com, wei.huang2@....com, terry.bowman@....com
Subject: Re: [PATCH v4 03/15] KVM: SVM: Detect X2APIC virtualization
(x2AVIC) support
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@...hat.com>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....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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