Re: [RFC PATCH v2 2/2] x86/virt/seamldr: Support multiple sigstruct pages

[Chao Gao <chao.gao@intel.com>]

On Thu, Nov 12, 2026 at 02:17:02AM +0800, Xu Yilun wrote:
>> Extend 'struct seamldr_params' to match the new ABI. The sigstruct
>> address list is already populated in a loop over all sigstruct pages, so
>> raising SEAMLDR_MAX_NR_SIG_PAGES is enough to fill the new slots
>
>As you mentioned [*], could you add a note maybe in populate_pa_list(),
>that chaining is only intended for the module binary, in case anyone
>gets lost when revisiting the sigstruct part.
>
>[*] https://lore.kernel.org/kvm/aumh_q8olQPwH0pe@intel.com/

Sure. Updated the comment above populate_pa_list() to:

/*
 * Given a vmalloc() allocation, write all of the backing physical
 * addresses to pa_list[]. Caller guarantees that the array is big
 * enough.
 *
 * If pa_list[] spans multiple pages, chain them by pointing the last
 * entry of each page to the next page. Note that a pa_list[] that
 * does not cross a page boundary, such as sigstruct_pages_pa_list[],
 * is never chained.
 */


>> @@ -166,6 +166,13 @@ static void populate_seamldr_params(struct seamldr_params *params,
>>  				    const u8 *mod, u32 mod_nr_pages)
>>  {
>>  	params->version		= 0;
>> +	/*
>> +	 * Use version 1 only for multi-page sigstructs, to stay
>> +	 * compatible with old P-SEAMLDRs that lack version 1 support.
>> +	 */
>> +	if (sig_nr_pages > 1)
>> +		params->version	= 1;
>
>If in future sig grows to more than 4 pages, can we stick to version 1?

That is up to the P-SEAMLDR ABI, but I will ask the P-SEAMLDR architects
to keep version 1 in that case.

>What's the planned boundary for sigstruct_pages_pa_list? I hope we don't
>further bump version on this.

The ABI allows four pages. The largest sigstruct today is two pages, so
there is already room for two more.

>
>> +
>>  	params->scenario	= SEAMLDR_SCENARIO_UPDATE;
>>  	params->module_nr_pages	= mod_nr_pages;
>>  
>> -- 
>> 2.52.0
>> 
>>