[PATCH v3 21/25] KVM: TDX: Add tdx_get_cmd() helper to get and validate sub-ioctl command

[Huang, Kai]

On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote:
> Add a helper to copy a kvm_tdx_cmd structure from userspace and verify
> that must-be-zero fields are indeed zero.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc at google.com>

Reviewed-by: Kai Huang <kai.huang at intel.com>

> ---
>  arch/x86/kvm/vmx/tdx.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 2e2dab89c98f..d5f810435f34 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -2761,20 +2761,25 @@ static int tdx_td_finalize(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
>  	return 0;
>  }
>  
> +static int tdx_get_cmd(void __user *argp, struct kvm_tdx_cmd *cmd)
> +{
> +	if (copy_from_user(cmd, argp, sizeof(*cmd)))
> +		return -EFAULT;
> +
> +	if (cmd->hw_error)
> +		return -EINVAL;

Nit: to me it's a little bit pity to lose the below comment:

	/*
	 * Userspace should never set hw_error. It is used to fill
	 * hardware-defined error by the kernel.
	 */