Re: [PATCH 2/5] KVM: nVMX: add KVM_CAP_HYPERV_ENLIGHTENED_VMCS capability

From: Liran Alon
Date: Thu Jun 14 2018 - 18:59:07 EST

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----- vkuznets@xxxxxxxxxx wrote:

> Enlightened VMCS is opt-in. The current version does not contain all
> fields supported by nested VMX so we must not advertise the
> corresponding VMX features if enlightened VMCS is enabled.
>
> Userspace is given the enlightened VMCS version supported by KVM as
> part of enabling KVM_CAP_HYPERV_ENLIGHTENED_VMCS. The version is to
> be advertised to the nested hypervisor, currently done via a cpuid
> leaf for Hyper-V.
>
> Suggested-by: Ladi Prosek <lprosek@xxxxxxxxxx>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 3 +
> arch/x86/kvm/svm.c | 9 +++
> arch/x86/kvm/vmx.c | 138
> ++++++++++++++++++++++------------------
> arch/x86/kvm/x86.c | 15 +++++
> include/uapi/linux/kvm.h | 1 +
> 5 files changed, 105 insertions(+), 61 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 0ebe659f2802..d7e8f7155d79 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1095,6 +1095,9 @@ struct kvm_x86_ops {
> int (*mem_enc_unreg_region)(struct kvm *kvm, struct kvm_enc_region
> *argp);
>
> int (*get_msr_feature)(struct kvm_msr_entry *entry);
> +
> + int (*nested_enable_evmcs)(struct kvm_vcpu *vcpu,
> + uint16_t *vmcs_version);
> };
>
> struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index d9305f1723f5..6dc42c870565 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -7009,6 +7009,13 @@ static int svm_unregister_enc_region(struct kvm
> *kvm,
> return ret;
> }
>
> +static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
> + uint16_t *vmcs_version)
> +{
> + /* Intel-only feature */
> + return -ENODEV;
> +}
> +
> static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
> .cpu_has_kvm_support = has_svm,
> .disabled_by_bios = is_disabled,
> @@ -7135,6 +7142,8 @@ static struct kvm_x86_ops svm_x86_ops
> __ro_after_init = {
> .mem_enc_op = svm_mem_enc_op,
> .mem_enc_reg_region = svm_register_enc_region,
> .mem_enc_unreg_region = svm_unregister_enc_region,
> +
> + .nested_enable_evmcs = nested_enable_evmcs,
> };
>
> static int __init svm_init(void)
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 48989f78be60..51749207cef1 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -648,6 +648,13 @@ struct nested_vmx {
>
> bool change_vmcs01_virtual_apic_mode;
>
> + /*
> + * Enlightened VMCS has been enabled. It does not mean that L1 has
> to
> + * use it. However, VMX features available to L1 will be limited
> based
> + * on what the enlightened VMCS supports.
> + */
> + bool enlightened_vmcs_enabled;
> +
> /* L2 must run next, and mustn't decide to exit to L1. */
> bool nested_run_pending;
>
> @@ -1186,6 +1193,49 @@ DEFINE_STATIC_KEY_FALSE(enable_evmcs);
>
> #define KVM_EVMCS_VERSION 1
>
> +/*
> + * Enlightened VMCSv1 doesn't support these:
> + *
> + * POSTED_INTR_NV = 0x00000002,
> + * GUEST_INTR_STATUS = 0x00000810,
> + * APIC_ACCESS_ADDR = 0x00002014,
> + * POSTED_INTR_DESC_ADDR = 0x00002016,
> + * EOI_EXIT_BITMAP0 = 0x0000201c,
> + * EOI_EXIT_BITMAP1 = 0x0000201e,
> + * EOI_EXIT_BITMAP2 = 0x00002020,
> + * EOI_EXIT_BITMAP3 = 0x00002022,
> + * GUEST_PML_INDEX = 0x00000812,
> + * PML_ADDRESS = 0x0000200e,
> + * VM_FUNCTION_CONTROL = 0x00002018,
> + * EPTP_LIST_ADDRESS = 0x00002024,
> + * VMREAD_BITMAP = 0x00002026,
> + * VMWRITE_BITMAP = 0x00002028,
> + *
> + * TSC_MULTIPLIER = 0x00002032,
> + * PLE_GAP = 0x00004020,
> + * PLE_WINDOW = 0x00004022,
> + * VMX_PREEMPTION_TIMER_VALUE = 0x0000482E,
> + * GUEST_IA32_PERF_GLOBAL_CTRL = 0x00002808,
> + * HOST_IA32_PERF_GLOBAL_CTRL = 0x00002c04,
> + *
> + * Currently unsupported in KVM:
> + * GUEST_IA32_RTIT_CTL = 0x00002814,
> + */
> +#define EVMCS1_UNSUPPORTED_PINCTRL (PIN_BASED_POSTED_INTR | \
> + PIN_BASED_VMX_PREEMPTION_TIMER)
> +#define EVMCS1_UNSUPPORTED_2NDEXEC \
> + (SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY | \
> + SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES | \
> + SECONDARY_EXEC_APIC_REGISTER_VIRT | \
> + SECONDARY_EXEC_ENABLE_PML | \
> + SECONDARY_EXEC_ENABLE_VMFUNC | \
> + SECONDARY_EXEC_SHADOW_VMCS | \
> + SECONDARY_EXEC_TSC_SCALING | \
> + SECONDARY_EXEC_PAUSE_LOOP_EXITING)
> +#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL
> (VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
> +#define EVMCS1_UNSUPPORTED_VMENTRY_CTRL
> (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
> +#define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)
> +
> #if IS_ENABLED(CONFIG_HYPERV)
> static bool __read_mostly enlightened_vmcs = true;
> module_param(enlightened_vmcs, bool, 0444);
> @@ -1278,69 +1328,12 @@ static void evmcs_load(u64 phys_addr)
>
> static void evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf)
> {
> - /*
> - * Enlightened VMCSv1 doesn't support these:
> - *
> - * POSTED_INTR_NV = 0x00000002,
> - * GUEST_INTR_STATUS = 0x00000810,
> - * APIC_ACCESS_ADDR = 0x00002014,
> - * POSTED_INTR_DESC_ADDR = 0x00002016,
> - * EOI_EXIT_BITMAP0 = 0x0000201c,
> - * EOI_EXIT_BITMAP1 = 0x0000201e,
> - * EOI_EXIT_BITMAP2 = 0x00002020,
> - * EOI_EXIT_BITMAP3 = 0x00002022,
> - */
> - vmcs_conf->pin_based_exec_ctrl &= ~PIN_BASED_POSTED_INTR;
> - vmcs_conf->cpu_based_2nd_exec_ctrl &=
> - ~SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY;
> - vmcs_conf->cpu_based_2nd_exec_ctrl &=
> - ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
> - vmcs_conf->cpu_based_2nd_exec_ctrl &=
> - ~SECONDARY_EXEC_APIC_REGISTER_VIRT;
> -
> - /*
> - * GUEST_PML_INDEX = 0x00000812,
> - * PML_ADDRESS = 0x0000200e,
> - */
> - vmcs_conf->cpu_based_2nd_exec_ctrl &= ~SECONDARY_EXEC_ENABLE_PML;
> + vmcs_conf->pin_based_exec_ctrl &= ~EVMCS1_UNSUPPORTED_PINCTRL;
> + vmcs_conf->cpu_based_2nd_exec_ctrl &= ~EVMCS1_UNSUPPORTED_2NDEXEC;
>
> - /* VM_FUNCTION_CONTROL = 0x00002018, */
> - vmcs_conf->cpu_based_2nd_exec_ctrl &=
> ~SECONDARY_EXEC_ENABLE_VMFUNC;
> + vmcs_conf->vmexit_ctrl &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
> + vmcs_conf->vmentry_ctrl &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
>
> - /*
> - * EPTP_LIST_ADDRESS = 0x00002024,
> - * VMREAD_BITMAP = 0x00002026,
> - * VMWRITE_BITMAP = 0x00002028,
> - */
> - vmcs_conf->cpu_based_2nd_exec_ctrl &= ~SECONDARY_EXEC_SHADOW_VMCS;
> -
> - /*
> - * TSC_MULTIPLIER = 0x00002032,
> - */
> - vmcs_conf->cpu_based_2nd_exec_ctrl &= ~SECONDARY_EXEC_TSC_SCALING;
> -
> - /*
> - * PLE_GAP = 0x00004020,
> - * PLE_WINDOW = 0x00004022,
> - */
> - vmcs_conf->cpu_based_2nd_exec_ctrl &=
> ~SECONDARY_EXEC_PAUSE_LOOP_EXITING;
> -
> - /*
> - * VMX_PREEMPTION_TIMER_VALUE = 0x0000482E,
> - */
> - vmcs_conf->pin_based_exec_ctrl &= ~PIN_BASED_VMX_PREEMPTION_TIMER;
> -
> - /*
> - * GUEST_IA32_PERF_GLOBAL_CTRL = 0x00002808,
> - * HOST_IA32_PERF_GLOBAL_CTRL = 0x00002c04,
> - */
> - vmcs_conf->vmexit_ctrl &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> - vmcs_conf->vmentry_ctrl &= ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> -
> - /*
> - * Currently unsupported in KVM:
> - * GUEST_IA32_RTIT_CTL = 0x00002814,
> - */

The creation of the EVMCS1_UNSUPPORTED_* macros and the refactor to evmcs_sanitize_exec_ctrls()
should be done in a separate patch in this series before this one.

> }
> #else /* !IS_ENABLED(CONFIG_HYPERV) */
> static inline void evmcs_write64(unsigned long field, u64 value) {}
> @@ -1354,6 +1347,27 @@ static inline void
> evmcs_sanitize_exec_ctrls(struct vmcs_config *vmcs_conf) {}
> static inline void evmcs_touch_msr_bitmap(void) {}
> #endif /* IS_ENABLED(CONFIG_HYPERV) */
>
> +static int nested_enable_evmcs(struct kvm_vcpu *vcpu,
> + uint16_t *vmcs_version)
> +{
> + struct vcpu_vmx *vmx = to_vmx(vcpu);
> +
> + /* We don't support disabling the feature for simplicity. */
> + if (vmx->nested.enlightened_vmcs_enabled)
> + return 0;
> +
> + vmx->nested.enlightened_vmcs_enabled = true;
> + *vmcs_version = (KVM_EVMCS_VERSION << 8) | 1;

Please add a comment here explaining the "<< 8) | 1" part.

> +
> + vmx->nested.msrs.pinbased_ctls_high &= ~EVMCS1_UNSUPPORTED_PINCTRL;
> + vmx->nested.msrs.entry_ctls_high &=
> ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
> + vmx->nested.msrs.exit_ctls_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
> + vmx->nested.msrs.secondary_ctls_high &=
> ~EVMCS1_UNSUPPORTED_2NDEXEC;
> + vmx->nested.msrs.vmfunc_controls &= ~EVMCS1_UNSUPPORTED_VMFUNC;
> +
> + return 0;
> +}
> +
> static inline bool is_exception_n(u32 intr_info, u8 vector)
> {
> return (intr_info & (INTR_INFO_INTR_TYPE_MASK |
> INTR_INFO_VECTOR_MASK |
> @@ -13039,6 +13053,8 @@ static struct kvm_x86_ops vmx_x86_ops
> __ro_after_init = {
> .pre_enter_smm = vmx_pre_enter_smm,
> .pre_leave_smm = vmx_pre_leave_smm,
> .enable_smi_window = enable_smi_window,
> +
> + .nested_enable_evmcs = nested_enable_evmcs,
> };
>
> static int __init vmx_init(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a57766b940a5..51488019dec2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2873,6 +2873,7 @@ int kvm_vm_ioctl_check_extension(struct kvm
> *kvm, long ext)
> case KVM_CAP_HYPERV_VP_INDEX:
> case KVM_CAP_HYPERV_EVENTFD:
> case KVM_CAP_HYPERV_TLBFLUSH:
> + case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> case KVM_CAP_PCI_SEGMENT:
> case KVM_CAP_DEBUGREGS:
> case KVM_CAP_X86_ROBUST_SINGLESTEP:
> @@ -3650,6 +3651,10 @@ static int kvm_set_guest_paused(struct kvm_vcpu
> *vcpu)
> static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> struct kvm_enable_cap *cap)
> {
> + int r;
> + uint16_t vmcs_version;
> + void __user *user_ptr;
> +
> if (cap->flags)
> return -EINVAL;
>
> @@ -3662,6 +3667,16 @@ static int kvm_vcpu_ioctl_enable_cap(struct
> kvm_vcpu *vcpu,
> return -EINVAL;
> return kvm_hv_activate_synic(vcpu, cap->cap ==
> KVM_CAP_HYPERV_SYNIC2);
> + case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
> + r = kvm_x86_ops->nested_enable_evmcs(vcpu, &vmcs_version);
> + if (!r) {
> + user_ptr = (void __user *)(uintptr_t)cap->args[0];
> + if (copy_to_user(user_ptr, &vmcs_version,
> + sizeof(vmcs_version)))
> + r = -EFAULT;
> + }
> + return r;
> +
> default:
> return -EINVAL;
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index b6270a3b38e9..5c4b79c1af19 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_GET_MSR_FEATURES 153
> #define KVM_CAP_HYPERV_EVENTFD 154
> #define KVM_CAP_HYPERV_TLBFLUSH 155
> +#define KVM_CAP_HYPERV_ENLIGHTENED_VMCS 156
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> --
> 2.14.4

Besides above comments,
Reviewed-By: Liran Alon <liran.alon@xxxxxxxxxx>

Next message: Zhouyang Jia: "[PATCH v3] scsi: xen-scsifront: add error handling for xenbus_printf"
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