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

[Xiaoyao Li]

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?

How about we pass in the struct page * and number into tdx_ext_mem_add() 
and construct the root page inside it?

> > so that we have a single central place of the comment to explain the kernel
> > design decision.
>
> How about I add a comment here to connect this wrapper to
> tdx_clflush_page():
>
> /*
>   * Unconditionally flush the pages regardless of CLFLUSH_BEFORE_ALLOC. Inherit
>   * the same decision as tdx_clflush_page().
>   */
> static void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
> ...

It works either. I don't have strong preference. Let's see if anyone 
else say something about it.