Re: [RFC PATCH 08/27] x86/virt/tdx: Add tdx_enable_ext() to enable of TDX Module Extensions

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Fri, 19 Sep 2025 07:22:17 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> From: Xu Yilun <yilun.xu@linux.intel.com>
> 
> tdx_enable() implements a simple state machine with @tdx_module_status to
> determine if TDX is already enabled, or failed to enable. Add another state
> to that enum (TDX_MODULE_INITIALIZED_EXT) to track if extensions have been enabled.
> 
> The extension initialization uses the new TDH.EXT.MEM.ADD and TDX.EXT.INIT
> seamcalls.
> 
> Note that this extension initialization does not impact existing in-flight
> SEAMCALLs that are not implemented by the extension. So only the first user
> of an extension-seamcall needs invoke this helper.
> 
> Co-developed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

A few more trivial comments.

> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index d47b2612c816..9d4cebace054 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c

> +
> +DEFINE_FREE(tdx_ext_mempool_free, struct tdx_page_array *, if (!IS_ERR_OR_NULL(_T)) tdx_ext_mempool_free(_T))
Very long line. Add a break somewhere!


> +/**
> + * tdx_enable_ext - Enable TDX module extensions.
> + *
> + * This function assumes the caller has done VMXON.
> + *
> + * This function can be called in parallel by multiple callers.
> + *
> + * Return 0 if TDX module extension is enabled successfully, otherwise error.
> + */
> +int tdx_enable_ext(void)
> +{
> +	int ret;
> +
> +	mutex_lock(&tdx_module_lock);
guard() perhaps which would make early returns an option if nothing esle
gets added after the switch.

> +
> +	switch (tdx_module_status) {
> +	case TDX_MODULE_INITIALIZED:
> +		ret = __tdx_enable_ext();
> +		break;
> +	case TDX_MODULE_INITIALIZED_EXT:
> +		ret = 0;
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	mutex_unlock(&tdx_module_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(tdx_enable_ext);