linux-kernel - Re: [RFC PATCH 02/21] x86/virt/tdx: Enhance tdh_mem_page

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Message-ID: <a7d0988d-037c-454f-bc6b-57e71b357488@linux.intel.com>
Date: Fri, 25 Apr 2025 14:51:18 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, x86@...nel.org, rick.p.edgecombe@...el.com,
 dave.hansen@...el.com, kirill.shutemov@...el.com, tabba@...gle.com,
 ackerleytng@...gle.com, quic_eberman@...cinc.com, michael.roth@....com,
 david@...hat.com, vannapurve@...gle.com, vbabka@...e.cz, jroedel@...e.de,
 thomas.lendacky@....com, pgonda@...gle.com, zhiquan1.li@...el.com,
 fan.du@...el.com, jun.miao@...el.com, ira.weiny@...el.com,
 isaku.yamahata@...el.com, xiaoyao.li@...el.com, chao.p.peng@...el.com
Subject: Re: [RFC PATCH 02/21] x86/virt/tdx: Enhance tdh_mem_page_aug() to
 support huge pages



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@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> ---
>   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;