Re: [PATCH v13 017/113] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl

[Zhi Wang]

On Sun, 12 Mar 2023 10:55:41 -0700
isaku.yamahata@xxxxxxxxx wrote:

> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> 
> Add a place holder function for TDX specific VM-scoped ioctl as mem_enc_op.
> TDX specific sub-commands will be added to retrieve/pass TDX specific
> parameters.  Make mem_enc_ioctl non-optional as it's not optional now.
                                                        ^ it is optional now.
> 
> KVM_MEMORY_ENCRYPT_OP was introduced for VM-scoped operations specific for
> guest state-protected VM.  It defined subcommands for technology-specific
> operations under KVM_MEMORY_ENCRYPT_OP.  Despite its name, the subcommands
> are not limited to memory encryption, but various technology-specific
> operations are defined.  It's natural to repurpose KVM_MEMORY_ENCRYPT_OP
> for TDX specific operations and define subcommands.
> 
> TDX requires VM-scoped TDX-specific operations for device model, for
> example, qemu.  Getting system-wide parameters, TDX-specific VM
> initialization.

^ Above two paragraphs are the "background" paragraphs, they should be in
the beginning of the patch comments.

> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |  2 +-
>  arch/x86/kvm/vmx/main.c            |  9 +++++++++
>  arch/x86/kvm/vmx/tdx.c             | 26 ++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/x86_ops.h         |  4 ++++
>  arch/x86/kvm/x86.c                 |  4 ----
>  5 files changed, 40 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index b46dcac078b2..58fbaa05fc8c 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -117,7 +117,7 @@ KVM_X86_OP(enter_smm)
>  KVM_X86_OP(leave_smm)
>  KVM_X86_OP(enable_smi_window)
>  #endif
> -KVM_X86_OP_OPTIONAL(dev_mem_enc_ioctl)
> +KVM_X86_OP(dev_mem_enc_ioctl)

I guess it should be KVM_X86_OP(mem_enc_ioctl) here.

>  KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
>  KVM_X86_OP_OPTIONAL(mem_enc_register_region)
>  KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 6a5d0c7a2950..8ddd263eeabc 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -50,6 +50,14 @@ static int vt_vm_init(struct kvm *kvm)
>  	return vmx_vm_init(kvm);
>  }
>  
> +static int vt_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
> +{
> +	if (!is_td(kvm))
> +		return -ENOTTY;
> +
> +	return tdx_vm_ioctl(kvm, argp);
> +}
> +
>  #define VMX_REQUIRED_APICV_INHIBITS		       \
>  (						       \
>         BIT(APICV_INHIBIT_REASON_DISABLE)|	       \
> @@ -203,6 +211,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>  	.vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,
>  
>  	.dev_mem_enc_ioctl = tdx_dev_ioctl,
> +	.mem_enc_ioctl = vt_mem_enc_ioctl,
>  };
>  
>  struct kvm_x86_init_ops vt_init_ops __initdata = {
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index b59d3081d061..d759028a698e 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -72,6 +72,32 @@ int tdx_dev_ioctl(void __user *argp)
>  	return 0;
>  }
>  
> +int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> +{
> +	struct kvm_tdx_cmd tdx_cmd;
> +	int r;
> +
> +	if (copy_from_user(&tdx_cmd, argp, sizeof(struct kvm_tdx_cmd)))
> +		return -EFAULT;
> +	if (tdx_cmd.error || tdx_cmd.unused)
> +		return -EINVAL;
> +
> +	mutex_lock(&kvm->lock);
> +
> +	switch (tdx_cmd.id) {
> +	default:
> +		r = -EINVAL;
> +		goto out;
> +	}
> +
> +	if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd)))
> +		r = -EFAULT;
> +
> +out:
> +	mutex_unlock(&kvm->lock);
> +	return r;
> +}
> +
>  static int __init tdx_module_setup(void)
>  {
>  	const struct tdsysinfo_struct *tdsysinfo;
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 78c5537e23a1..c70749114e9e 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -142,11 +142,15 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops);
>  int tdx_hardware_enable(void);
>  bool tdx_is_vm_type_supported(unsigned long type);
>  int tdx_dev_ioctl(void __user *argp);
> +
> +int tdx_vm_ioctl(struct kvm *kvm, void __user *argp);
>  #else
>  static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -ENOSYS; }
>  static inline int tdx_hardware_enable(void) { return -EOPNOTSUPP; }
>  static inline bool tdx_is_vm_type_supported(unsigned long type) { return false; }
>  static inline int tdx_dev_ioctl(void __user *argp) { return -EOPNOTSUPP; };
> +
> +static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOPNOTSUPP; }
>  #endif
>  
>  #endif /* __KVM_X86_VMX_X86_OPS_H */
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a3dc32e33aca..8687623929c3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6978,10 +6978,6 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  		goto out;
>  	}
>  	case KVM_MEMORY_ENCRYPT_OP: {
> -		r = -ENOTTY;
> -		if (!kvm_x86_ops.mem_enc_ioctl)
> -			goto out;
> -
>  		r = static_call(kvm_x86_mem_enc_ioctl)(kvm, argp);
>  		break;
>  	}