Re: [PATCH v1 15/23] KVM: nVMX: Add support for the secondary VM exit controls

Vitaly Kuznetsov
2023-11-20T15:53:04Z

Xin Li <xin3.li@intel.com> writes:

> Enable the secondary VM exit controls to prepare for nested FRED.
>
> Tested-by: Shan Kang <shan.kang@intel.com>
> Signed-off-by: Xin Li <xin3.li@intel.com>
> ---
> Documentation/virt/kvm/x86/nested-vmx.rst | 1 +
> arch/x86/include/asm/hyperv-tlfs.h | 1 +
> arch/x86/kvm/vmx/capabilities.h | 1 +
> arch/x86/kvm/vmx/hyperv.c | 18 +++++++++++++++++-
> arch/x86/kvm/vmx/nested.c | 18 +++++++++++++++++-
> arch/x86/kvm/vmx/vmcs12.c | 1 +
> arch/x86/kvm/vmx/vmcs12.h | 2 ++
> arch/x86/kvm/x86.h | 2 +-
> 8 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/x86/nested-vmx.rst b/Documentation/virt/kvm/x86/nested-vmx.rst
> index ac2095d41f02..e64ef231f310 100644
> --- a/Documentation/virt/kvm/x86/nested-vmx.rst
> +++ b/Documentation/virt/kvm/x86/nested-vmx.rst
> @@ -217,6 +217,7 @@ struct shadow_vmcs is ever changed.
> u16 host_fs_selector;
> u16 host_gs_selector;
> u16 host_tr_selector;
> + u64 secondary_vm_exit_controls;
> };
>
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 2ff26f53cd62..299554708e37 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -616,6 +616,7 @@ struct hv_enlightened_vmcs {
> u64 host_ssp;
> u64 host_ia32_int_ssp_table_addr;
> u64 padding64_6;
> + u64 secondary_vm_exit_controls;

(I think Jeremi has asked a similar question but just to be sure)

This doesn't seem to be present in the currently available TLFS version
e.g. here:
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/datatypes/hv_vmx_enlightened_vmcs

That wouldn't be the first time when TLFS lags behind but as I don't see
anyone from Microsoft signing this off, let me ask: where did you get
this information and, in case it came from someone @microsoft.com, can
we get their sign-off on the patch?

> } __packed;
>
> #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE 0
> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
> index e8f3ad0f79ee..caf38a54856c 100644
> --- a/arch/x86/kvm/vmx/capabilities.h
> +++ b/arch/x86/kvm/vmx/capabilities.h
> @@ -38,6 +38,7 @@ struct nested_vmx_msrs {
> u32 pinbased_ctls_high;
> u32 exit_ctls_low;
> u32 exit_ctls_high;
> + u64 secondary_exit_ctls;
> u32 entry_ctls_low;
> u32 entry_ctls_high;
> u32 misc_low;
> diff --git a/arch/x86/kvm/vmx/hyperv.c b/arch/x86/kvm/vmx/hyperv.c
> index 313b8bb5b8a7..b8cd53601a00 100644
> --- a/arch/x86/kvm/vmx/hyperv.c
> +++ b/arch/x86/kvm/vmx/hyperv.c
> @@ -103,7 +103,10 @@
> VM_EXIT_LOAD_IA32_EFER | \
> VM_EXIT_CLEAR_BNDCFGS | \
> VM_EXIT_PT_CONCEAL_PIP | \
> - VM_EXIT_CLEAR_IA32_RTIT_CTL)
> + VM_EXIT_CLEAR_IA32_RTIT_CTL | \
> + VM_EXIT_ACTIVATE_SECONDARY_CONTROLS)
> +
> +#define EVMCS1_SUPPORTED_VMEXIT_CTRL2 (0ULL)
>
> #define EVMCS1_SUPPORTED_VMENTRY_CTRL \
> (VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR | \
> @@ -315,6 +318,8 @@ const struct evmcs_field vmcs_field_to_evmcs_1[] = {
> HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP1),
> EVMCS1_FIELD(VM_EXIT_CONTROLS, vm_exit_controls,
> HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP1),
> + EVMCS1_FIELD(SECONDARY_VM_EXIT_CONTROLS, secondary_vm_exit_controls,
> + HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP1),
> EVMCS1_FIELD(SECONDARY_VM_EXEC_CONTROL, secondary_vm_exec_control,
> HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP1),
> EVMCS1_FIELD(GUEST_ES_LIMIT, guest_es_limit,
> @@ -464,6 +469,7 @@ enum evmcs_revision {
>
> enum evmcs_ctrl_type {
> EVMCS_EXIT_CTRLS,
> + EVMCS_2NDEXIT,
> EVMCS_ENTRY_CTRLS,
> EVMCS_EXEC_CTRL,
> EVMCS_2NDEXEC,
> @@ -477,6 +483,9 @@ static const u32 evmcs_supported_ctrls[NR_EVMCS_CTRLS][NR_EVMCS_REVISIONS] = {
> [EVMCS_EXIT_CTRLS] = {
> [EVMCSv1_LEGACY] = EVMCS1_SUPPORTED_VMEXIT_CTRL,
> },
> + [EVMCS_2NDEXIT] = {
> + [EVMCSv1_LEGACY] = EVMCS1_SUPPORTED_VMEXIT_CTRL2,
> + },
> [EVMCS_ENTRY_CTRLS] = {
> [EVMCSv1_LEGACY] = EVMCS1_SUPPORTED_VMENTRY_CTRL,
> },

What's the desired effect here? I.e. why exposing
VM_EXIT_ACTIVATE_SECONDARY_CONTROLS when none of the controls are going
to be exposed?

> @@ -539,6 +548,9 @@ void nested_evmcs_filter_control_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *
> supported_ctrls &= ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> ctl_high &= supported_ctrls;
> break;
> + case MSR_IA32_VMX_EXIT_CTLS2:
> + ctl_low &= evmcs_get_supported_ctls(EVMCS_2NDEXIT);
> + break;
> case MSR_IA32_VMX_ENTRY_CTLS:
> case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
> supported_ctrls = evmcs_get_supported_ctls(EVMCS_ENTRY_CTRLS);
> @@ -589,6 +601,10 @@ int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
> vmcs12->vm_exit_controls)))
> return -EINVAL;
>
> + if (CC(!nested_evmcs_is_valid_controls(EVMCS_2NDEXIT,
> + vmcs12->secondary_vm_exit_controls)))
> + return -EINVAL;
> +
> if (CC(!nested_evmcs_is_valid_controls(EVMCS_ENTRY_CTRLS,
> vmcs12->vm_entry_controls)))
> return -EINVAL;
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index ff07d6e736a2..d6341845df43 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1411,6 +1411,7 @@ int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
> case MSR_IA32_VMX_PINBASED_CTLS:
> case MSR_IA32_VMX_PROCBASED_CTLS:
> case MSR_IA32_VMX_EXIT_CTLS:
> + case MSR_IA32_VMX_EXIT_CTLS2:
> case MSR_IA32_VMX_ENTRY_CTLS:
> /*
> * The "non-true" VMX capability MSRs are generated from the
> @@ -1489,6 +1490,9 @@ int vmx_get_vmx_msr(struct nested_vmx_msrs *msrs, u32 msr_index, u64 *pdata)
> if (msr_index == MSR_IA32_VMX_EXIT_CTLS)
> *pdata |= VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR;
> break;
> + case MSR_IA32_VMX_EXIT_CTLS2:
> + *pdata = msrs->secondary_exit_ctls;
> + break;
> case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
> case MSR_IA32_VMX_ENTRY_CTLS:
> *pdata = vmx_control_msr(
> @@ -1692,6 +1696,8 @@ static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx, u32 hv_clean_fields
> vmcs12->pin_based_vm_exec_control =
> evmcs->pin_based_vm_exec_control;
> vmcs12->vm_exit_controls = evmcs->vm_exit_controls;
> + vmcs12->secondary_vm_exit_controls =
> + evmcs->secondary_vm_exit_controls;
> vmcs12->secondary_vm_exec_control =
> evmcs->secondary_vm_exec_control;
> }
> @@ -1894,6 +1900,7 @@ static void copy_vmcs12_to_enlightened(struct vcpu_vmx *vmx)
> * evmcs->vmcs_link_pointer = vmcs12->vmcs_link_pointer;
> * evmcs->pin_based_vm_exec_control = vmcs12->pin_based_vm_exec_control;
> * evmcs->vm_exit_controls = vmcs12->vm_exit_controls;
> + * evmcs->secondary_vm_exit_controls = vmcs12->secondary_vm_exit_controls;
> * evmcs->secondary_vm_exec_control = vmcs12->secondary_vm_exec_control;
> * evmcs->page_fault_error_code_mask =
> * vmcs12->page_fault_error_code_mask;
> @@ -2411,6 +2418,11 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct loaded_vmcs *vmcs0
> exec_control &= ~VM_EXIT_LOAD_IA32_EFER;
> vm_exit_controls_set(vmx, exec_control);
>
> + if (exec_control & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS) {
> + exec_control = __secondary_vm_exit_controls_get(vmcs01);
> + secondary_vm_exit_controls_set(vmx, exec_control);
> + }
> +
> /*
> * Interrupt/Exception Fields
> */
> @@ -6819,13 +6831,17 @@ static void nested_vmx_setup_exit_ctls(struct vmcs_config *vmcs_conf,
> VM_EXIT_HOST_ADDR_SPACE_SIZE |
> #endif
> VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT |
> - VM_EXIT_CLEAR_BNDCFGS;
> + VM_EXIT_CLEAR_BNDCFGS | VM_EXIT_ACTIVATE_SECONDARY_CONTROLS;
> msrs->exit_ctls_high |=
> VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
> VM_EXIT_LOAD_IA32_EFER | VM_EXIT_SAVE_IA32_EFER |
> VM_EXIT_SAVE_VMX_PREEMPTION_TIMER | VM_EXIT_ACK_INTR_ON_EXIT |
> VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
>
> + /* secondary exit controls */
> + if (msrs->exit_ctls_high & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS)
> + rdmsrl(MSR_IA32_VMX_EXIT_CTLS2, msrs->secondary_exit_ctls);
> +
> /* We support free control of debug control saving. */
> msrs->exit_ctls_low &= ~VM_EXIT_SAVE_DEBUG_CONTROLS;
> }
> diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
> index 106a72c923ca..98457d7b2b23 100644
> --- a/arch/x86/kvm/vmx/vmcs12.c
> +++ b/arch/x86/kvm/vmx/vmcs12.c
> @@ -73,6 +73,7 @@ const unsigned short vmcs12_field_offsets[] = {
> FIELD(PAGE_FAULT_ERROR_CODE_MATCH, page_fault_error_code_match),
> FIELD(CR3_TARGET_COUNT, cr3_target_count),
> FIELD(VM_EXIT_CONTROLS, vm_exit_controls),
> + FIELD(SECONDARY_VM_EXIT_CONTROLS, secondary_vm_exit_controls),
> FIELD(VM_EXIT_MSR_STORE_COUNT, vm_exit_msr_store_count),
> FIELD(VM_EXIT_MSR_LOAD_COUNT, vm_exit_msr_load_count),
> FIELD(VM_ENTRY_CONTROLS, vm_entry_controls),
> diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
> index 01936013428b..f50f897b9b5f 100644
> --- a/arch/x86/kvm/vmx/vmcs12.h
> +++ b/arch/x86/kvm/vmx/vmcs12.h
> @@ -185,6 +185,7 @@ struct __packed vmcs12 {
> u16 host_gs_selector;
> u16 host_tr_selector;
> u16 guest_pml_index;
> + u64 secondary_vm_exit_controls;
> };
>
> /*
> @@ -358,6 +359,7 @@ static inline void vmx_check_vmcs12_offsets(void)
> CHECK_OFFSET(host_gs_selector, 992);
> CHECK_OFFSET(host_tr_selector, 994);
> CHECK_OFFSET(guest_pml_index, 996);
> + CHECK_OFFSET(secondary_vm_exit_controls, 998);
> }
>
> extern const unsigned short vmcs12_field_offsets[];
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 63e543c6834b..96ad139adc3f 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -47,7 +47,7 @@ void kvm_spurious_fault(void);
> * associated feature that KVM supports for nested virtualization.
> */
> #define KVM_FIRST_EMULATED_VMX_MSR MSR_IA32_VMX_BASIC
> -#define KVM_LAST_EMULATED_VMX_MSR MSR_IA32_VMX_VMFUNC
> +#define KVM_LAST_EMULATED_VMX_MSR MSR_IA32_VMX_EXIT_CTLS2
>
> #define KVM_DEFAULT_PLE_GAP 128
> #define KVM_VMX_DEFAULT_PLE_WINDOW 4096

--
Vitaly