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

[Binbin Wu]

On 4/24/2025 11:04 AM, 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);
> +	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) ||
> +	    (folio_page_idx(folio, page) + nr_pages > folio_nr_pages(folio)))
> +		return -EINVAL;
> +
> +	while (nr_pages--)
> +		tdx_clflush_page(nth_page(page, idx++));
Is the following better to save a variable?

while (nr_pages)
    tdx_clflush_page(nth_page(page, --nr_pages));


> +
>   	ret = seamcall_ret(TDH_MEM_PAGE_AUG, &args);
>   
>   	*ext_err1 = args.rcx;