[PATCH v3 6/6] x86/virt/tdx: Support DPAMT when adding memory for the extensions

[Xu Yilun]

The TDX module uses Physical Address Metadata Table (PAMT) to track some
state for each page of physical memory that it might use. 3 levels of
PAMTs are used to track pages of different sizes - 1GB, 2MB and 4KB.
Dynamic PAMT (DPAMT) allows saving memory by allocating 4KB PAMT
dynamically, while the 1GB and 2MB levels remain allocated on TDX module
initialization. The kernel has helpers to install 4K DPAMT.

Although the memory for the extensions is tens of megabytes and the host
allocates it in a large chunk, the TDX module accepts it at 4K
granularity. Thus the host has to install 4K DPAMT for each page of it.

Call tdx_pamt_get() for each page before adding it to TDX module.
Normally, these operations should not fail, and if they do,
intentionally keep the error handling as simple as before - leak all
pages, including the installed 4K DPAMT metadata.

Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
---
v3:
 - New patch
---
 arch/x86/virt/vmx/tdx/tdx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 5d5f9da1ab02..27a7039ee443 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1330,8 +1330,15 @@ static __init int tdx_ext_mem_setup(void)
 		struct page *chunk = page + added_pages;
 		unsigned int i;
 
-		for (i = 0; i < chunk_pages; i++)
+		for (i = 0; i < chunk_pages; i++) {
+			ret = tdx_pamt_get(page_to_pfn(chunk + i), NULL);
+			if (ret) {
+				WARN(1, "DPAMT setup error for extensions, stranded all pages\n");
+				goto out_free_hpa_list;
+			}
+
 			hpa_list->phys[i] = page_to_phys(chunk + i);
+		}
 
 		ret = tdx_ext_mem_add(hpa_list, chunk_pages);
 		if (ret) {

-- 
2.25.1