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

[Yan Zhao]

On Thu, May 15, 2025 at 10:16:58AM +0800, Chao Gao wrote:
> 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);
> >+	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;
> 
> Returning -EINVAL looks incorrect as the return type is u64.
Good catch. Thanks!
I'll think about how to handle it. Looks it could be dropped if we trust KVM.


> >+	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
> >