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

[Xiaoyao Li]

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@xxxxxxxxx/

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.