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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Xin Li <xin3.li@intel.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hyperv@vger.kernel.org, linux-kselftest@vger.kernel.org
Cc:     seanjc@google.com, pbonzini@redhat.com, corbet@lwn.net,
        kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
        decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
        hpa@zytor.com, peterz@infradead.org, ravi.v.shankar@intel.com
Subject: Re: [PATCH v1 15/23] KVM: nVMX: Add support for the secondary VM
 exit controls
In-Reply-To: <20231108183003.5981-16-xin3.li@intel.com>
References: <20231108183003.5981-1-xin3.li@intel.com>
 <20231108183003.5981-16-xin3.li@intel.com>
Date:   Mon, 20 Nov 2023 16:52:58 +0100
Message-ID: <87y1espgkl.fsf@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

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