Re: [PATCH v17 025/116] KVM: TDX: allocate/free TDX vcpu structure

[Binbin Wu <binbin.wu@linux.intel.com>]

On 11/7/2023 10:55 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> The next step of TDX guest creation is to create vcpu.  Allocate TDX vcpu
> structures, initialize it that doesn't require TDX SEAMCALL.
Didn't see any allocation happens for TDX in this patch.


>   TDX specific
> vcpu initialization will be implemented as independent KVM_TDX_INIT_VCPU
> so that when error occurs it's easy to determine which component has the
> issue, KVM or TDX.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> v15 -> v16:
> - Add AMX support as the KVM upstream supports it.
> ---
>   arch/x86/kvm/vmx/main.c    | 44 ++++++++++++++++++++++++++++++----
>   arch/x86/kvm/vmx/tdx.c     | 49 ++++++++++++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/x86_ops.h | 10 ++++++++
>   arch/x86/kvm/x86.c         |  2 ++
>   4 files changed, 101 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index c8213d6ea301..f60de0232f7f 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -98,6 +98,42 @@ static void vt_vm_free(struct kvm *kvm)
>   		tdx_vm_free(kvm);
>   }
>   
> +static int vt_vcpu_precreate(struct kvm *kvm)
> +{
> +	if (is_td(kvm))
> +		return 0;
> +
> +	return vmx_vcpu_precreate(kvm);
> +}
> +
> +static int vt_vcpu_create(struct kvm_vcpu *vcpu)
> +{
> +	if (is_td_vcpu(vcpu))
> +		return tdx_vcpu_create(vcpu);
> +
> +	return vmx_vcpu_create(vcpu);
> +}
> +
> +static void vt_vcpu_free(struct kvm_vcpu *vcpu)
> +{
> +	if (is_td_vcpu(vcpu)) {
> +		tdx_vcpu_free(vcpu);
> +		return;
> +	}
> +
> +	vmx_vcpu_free(vcpu);
> +}

I'm wondering for such wrapper functions without a return value,
is the following style cleaner?
It can save two lines of code.

+static void vt_vcpu_free(struct kvm_vcpu *vcpu)
+{
+    if (is_td_vcpu(vcpu))
+        tdx_vcpu_free(vcpu);
+    else
+        vmx_vcpu_free(vcpu);
+}


> +
> +static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> +{
> +	if (is_td_vcpu(vcpu)) {
> +		tdx_vcpu_reset(vcpu, init_event);
> +		return;
> +	}
> +
> +	vmx_vcpu_reset(vcpu, init_event);
> +}
> +
ditto

>   static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
>   {
>   	if (!is_td(kvm))
> @@ -136,10 +172,10 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>   	.vm_destroy = vt_vm_destroy,
>   	.vm_free = vt_vm_free,
>   
> -	.vcpu_precreate = vmx_vcpu_precreate,
> -	.vcpu_create = vmx_vcpu_create,
> -	.vcpu_free = vmx_vcpu_free,
> -	.vcpu_reset = vmx_vcpu_reset,
> +	.vcpu_precreate = vt_vcpu_precreate,
> +	.vcpu_create = vt_vcpu_create,
> +	.vcpu_free = vt_vcpu_free,
> +	.vcpu_reset = vt_vcpu_reset,
>   
>   	.prepare_switch_to_guest = vmx_prepare_switch_to_guest,
>   	.vcpu_load = vmx_vcpu_load,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 51aa114feb86..b7f8ac4b9f95 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -335,6 +335,55 @@ int tdx_vm_init(struct kvm *kvm)
>   	return 0;
>   }
>   
> +int tdx_vcpu_create(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
> +
> +	/*
> +	 * On cpu creation, cpuid entry is blank.  Forcibly enable
> +	 * X2APIC feature to allow X2APIC.
> +	 * Because vcpu_reset() can't return error, allocation is done here.
> +	 */
> +	WARN_ON_ONCE(vcpu->arch.cpuid_entries);
> +	WARN_ON_ONCE(vcpu->arch.cpuid_nent);
> +
> +	/* TDX only supports x2APIC, which requires an in-kernel local APIC. */
> +	if (!vcpu->arch.apic)
> +		return -EINVAL;
> +
> +	fpstate_set_confidential(&vcpu->arch.guest_fpu);
> +
> +	vcpu->arch.efer = EFER_SCE | EFER_LME | EFER_LMA | EFER_NX;
> +
> +	vcpu->arch.cr0_guest_owned_bits = -1ul;
> +	vcpu->arch.cr4_guest_owned_bits = -1ul;
> +
> +	vcpu->arch.tsc_offset = to_kvm_tdx(vcpu->kvm)->tsc_offset;
> +	vcpu->arch.l1_tsc_offset = vcpu->arch.tsc_offset;
> +	vcpu->arch.guest_state_protected =
> +		!(to_kvm_tdx(vcpu->kvm)->attributes & TDX_TD_ATTRIBUTE_DEBUG);
> +
> +	if ((kvm_tdx->xfam & XFEATURE_MASK_XTILE) == XFEATURE_MASK_XTILE)
> +		vcpu->arch.xfd_no_write_intercept = true;
> +
> +	return 0;
> +}
> +
> +void tdx_vcpu_free(struct kvm_vcpu *vcpu)
> +{
> +	/* This is stub for now.  More logic will come. */
> +}
> +
> +void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> +{
> +
> +	/* Ignore INIT silently because TDX doesn't support INIT event. */
> +	if (init_event)
> +		return;
> +
> +	/* This is stub for now. More logic will come here. */
> +}
> +
>   static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
>   {
>   	struct kvm_tdx_capabilities __user *user_caps;
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index ffba64008682..ebb963848316 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -144,7 +144,12 @@ int tdx_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
>   int tdx_vm_init(struct kvm *kvm);
>   void tdx_mmu_release_hkid(struct kvm *kvm);
>   void tdx_vm_free(struct kvm *kvm);
> +
>   int tdx_vm_ioctl(struct kvm *kvm, void __user *argp);
> +
> +int tdx_vcpu_create(struct kvm_vcpu *vcpu);
> +void tdx_vcpu_free(struct kvm_vcpu *vcpu);
> +void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
>   #else
>   static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -EOPNOTSUPP; }
>   static inline void tdx_hardware_unsetup(void) {}
> @@ -158,7 +163,12 @@ static inline int tdx_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
>   static inline int tdx_vm_init(struct kvm *kvm) { return -EOPNOTSUPP; }
>   static inline void tdx_mmu_release_hkid(struct kvm *kvm) {}
>   static inline void tdx_vm_free(struct kvm *kvm) {}
> +
>   static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOPNOTSUPP; }
> +
> +static inline int tdx_vcpu_create(struct kvm_vcpu *vcpu) { return -EOPNOTSUPP; }
> +static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {}
> +static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {}
>   #endif
>   
>   #endif /* __KVM_X86_VMX_X86_OPS_H */
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 191ac1e0d96d..0414822e7a03 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -502,6 +502,7 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>   	kvm_recalculate_apic_map(vcpu->kvm);
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(kvm_set_apic_base);
>   
>   /*
>    * Handle a fault on a hardware virtualization (VMX or SVM) instruction.
> @@ -12430,6 +12431,7 @@ bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu)
>   {
>   	return vcpu->kvm->arch.bsp_vcpu_id == vcpu->vcpu_id;
>   }
> +EXPORT_SYMBOL_GPL(kvm_vcpu_is_reset_bsp);
>   
>   bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
>   {