Re: [PATCH 04/15] x86/virt/tdx: Enable the Extensions right after basic TDX Module init

[Kishen Maloor <kishen.maloor@intel.com>]

On 5/21/26 8:41 PM, Xu Yilun wrote:
> The detailed initialization flow for TDX Module Extensions has been
> fully implemented. Enable the flow after basic TDX Module
> initialization.
> 
> Theoretically, the Extensions doesn't need to be enabled right after
> basic TDX initialization. It could be enabled right before the first
> Extension SEAMCALL is issued. That would save or postpone memory usage.
> But it isn't worth the complexity, the needs for the Extensions are vast
> but the savings are little for a typical TDX capable system (about
> 0.001% of memory). So the Linux decision is to just enable it along with
> the basic TDX.
> 
> Note that the Extensions initialization flow will still not start if no
> add-on features require Extensions. The enabling of add-on features will
> be in later patches. Until then, the system hasn't consumed extra memory.
> 
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> ---
>   arch/x86/virt/vmx/tdx/tdx.c | 16 ++++++++++------
>   1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index ff2b96c20d2b..dad5ec642723 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -1180,7 +1180,7 @@ static __init int init_tdmrs(struct tdmr_info_list *tdmr_list)
>   	return 0;
>   }
>   
> -static void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
> +static __init void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
>   {
>   	u64 *entries = page_to_virt(root);
>   	int i;
> @@ -1193,7 +1193,7 @@ static void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
>   #define HPA_LIST_INFO_PFN		GENMASK_U64(51, 12)
>   #define HPA_LIST_INFO_LAST_ENTRY	GENMASK_U64(63, 55)
>   
> -static u64 to_hpa_list_info(struct page *root, unsigned int nr_pages)
> +static __init u64 to_hpa_list_info(struct page *root, unsigned int nr_pages)
>   {
>   	return FIELD_PREP(HPA_LIST_INFO_FIRST_ENTRY, 0) |
>   	       FIELD_PREP(HPA_LIST_INFO_PFN, page_to_pfn(root)) |
> @@ -1201,7 +1201,7 @@ static u64 to_hpa_list_info(struct page *root, unsigned int nr_pages)
>   }
>   
>   /* Initialize the TDX Module Extensions then Extension-SEAMCALLs can be used */
> -static int tdx_ext_init(void)
> +static __init int tdx_ext_init(void)
>   {
>   	struct tdx_module_args args = {};
>   	u64 r;
> @@ -1216,7 +1216,7 @@ static int tdx_ext_init(void)
>   	return 0;
>   }
>   
> -static int tdx_ext_mem_add(struct page *root, unsigned int nr_pages)
> +static __init int tdx_ext_mem_add(struct page *root, unsigned int nr_pages)
>   {
>   	struct tdx_module_args args = {
>   		.rcx = to_hpa_list_info(root, nr_pages),
> @@ -1240,7 +1240,7 @@ static int tdx_ext_mem_add(struct page *root, unsigned int nr_pages)
>   	return 0;
>   }
>   
> -static int tdx_ext_mem_setup(void)
> +static __init int tdx_ext_mem_setup(void)
>   {
>   	unsigned int nr_pages;
>   	struct page *page;
> @@ -1301,7 +1301,7 @@ static int tdx_ext_mem_setup(void)
>   	return ret;
>   }
>   
> -static int __maybe_unused init_tdx_ext(void)
> +static __init int init_tdx_ext(void)
>   {
>   	int ret;
>   
> @@ -1373,6 +1373,10 @@ static __init int init_tdx_module(void)
>   	if (ret)
>   		goto err_reset_pamts;
>   
> +	ret = init_tdx_ext();
> +	if (ret)
> +		goto err_reset_pamts;

Is it a reasonable policy to fail TDX bringup entirely upon failing
initialization of extensions (which are "add-on features")?

The handling of tdx_quote_init() in Patch 6 suggests a more
best-effort approach.

> +
>   	pr_info("%lu KB allocated for PAMT\n", tdmrs_count_pamt_kb(&tdx_tdmr_list));
>   
>   out_put_tdxmem: