Re: [PATCH 02/15] x86/virt/tdx: Add extra memory to TDX Module for Extensions

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 5/27/2026 3:32 PM, Xu Yilun wrote:
> On Wed, May 27, 2026 at 02:38:27PM +0800, Xiaoyao Li wrote:
>> On 5/27/2026 11:47 AM, Xu Yilun wrote:
>>>>> +static void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
>>>>> +{
>>>>> +	u64 *entries = page_to_virt(root);
>>>>> +	int i;
>>>>> +
>>>>> +	for (i = 0; i < nr_pages; i++)
>>>>> +		clflush_cache_range(__va(entries[i]), PAGE_SIZE);
>>>>
>>>> Is the page flush only needed when CLFLUSH_BEFORE_ALLOC is true?
>>>>
>>>> If so, it inherits the same decision to always flush as what
>>>
>>> Yes it is basically the same as tdx_clflush_page().
>>>
>>>> tdx_clflush_page() did. Then, any chance we can use tdx_clflush_page() here
>>>
>>> But I don't think we should convert hpa/page/va back and forth just for
>>> re-using one line of code.
>>
>> Because we want/need to flush page as late as possible so that the page
>> flush needs to happen right before SEAMCALL?
> 
> I think so. Let the flushing be part of the tdh call semantic.
> 
>>
>> How about we pass in the struct page * and number into tdx_ext_mem_add() and
>> construct the root page inside it?
> 
> I assume you don't suggest allocate root page inside the call, then we
> need 3 parameters for the HPA_LIST_INFO:
> 
>    struct page *, unsigned int nr_pages, struct page *root
> 
> which I think too much.

yeah, sort of.

> I think your concern is to try not to introduce another tdx_clflush_
> variant, but I believe this will happen, pfn based memory description is
> on the way:
> 
> https://lore.kernel.org/all/20260430014929.24210-1-yan.y.zhao@intel.com/

I don't object the variant of tdx_clflush_hpa_list(), but suggest if 
tdx_clflush_page() can be used instead of raw clflush_cache_range()

Maybe we can try to put tdx_clflush_hpa_list() along with 
tdx_clflush_page() and tdx_clflush_pfn()? This way, I think we can save 
the separate comment.