Re: [RFC PATCH 02/21] x86/virt/tdx: Enhance tdh_mem_page_aug() to support huge pages

[Kirill A. Shutemov]

On Thu, Apr 24, 2025 at 11:04:28AM +0800, Yan Zhao wrote:
> Enhance the SEAMCALL wrapper tdh_mem_page_aug() to support huge pages.
> 
> Verify the validity of the level and ensure that the mapping range is fully
> contained within the page folio.
> 
> As a conservative solution, perform CLFLUSH on all pages to be mapped into
> the TD before invoking the SEAMCALL TDH_MEM_PAGE_AUG. This ensures that any
> dirty cache lines do not write back later and clobber TD memory.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index f5e2a937c1e7..a66d501b5677 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -1595,9 +1595,18 @@ u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u
>  		.rdx = tdx_tdr_pa(td),
>  		.r8 = page_to_phys(page),
>  	};
> +	unsigned long nr_pages = 1 << (level * 9);

PTE_SHIFT.

> +	struct folio *folio = page_folio(page);
> +	unsigned long idx = 0;
>  	u64 ret;
>  
> -	tdx_clflush_page(page);
> +	if (!(level >= TDX_PS_4K && level < TDX_PS_NR) ||

Do we even need this check?

> +	    (folio_page_idx(folio, page) + nr_pages > folio_nr_pages(folio)))
> +		return -EINVAL;
> +
> +	while (nr_pages--)
> +		tdx_clflush_page(nth_page(page, idx++));
> +
>  	ret = seamcall_ret(TDH_MEM_PAGE_AUG, &args);
>  
>  	*ext_err1 = args.rcx;
> -- 
> 2.43.2
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov