[PATCH v2 04/31] x86/virt/tdx: Support allocating contiguous pages for tdx_page_array

Xu Yilun
2026-03-27T16:22:48Z

The current tdx_page_array implementation allocates scattered order-0
pages. However, some TDX Module operations benefit from contiguous
physical memory. E.g. Enabling TDX Module Extensions (an optional TDX
feature) requires ~50MB memory and never returns. Such allocation
would at worst cause ~25GB permanently fragmented memory if each
allocated page is from a different 2M region.

Support allocating contiguous pages for tdx_page_array by making the
allocation method configurable. Change the tdx_page_array_alloc() to
accept a custom allocation function pointer and a context parameter.
Wrap the specific allocation into a tdx_page_array_alloc_contig()
helper.

The foreseeable caller will allocate ~50MB memory with this helper,
exceeding the maximum HPAs (512) a root page can hold, the typical usage
will be:

- struct tdx_page_array *array = tdx_page_array_alloc_contig(nr_pages);
- for each 512-page bulk
- tdx_page_array_populate(array, offset);
- seamcall(TDH_XXX_ADD, array, ...);

The configurable allocation method would also benefit more
tdx_page_array usages. TDX Module may require more specific memory
layouts encoded in the root page. Will introduce them in following
patches.

Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
---
arch/x86/virt/vmx/tdx/tdx.c | 42 +++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index a3021e7e2490..6c4ed80e8e5a 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -289,7 +289,8 @@ static void tdx_free_pages_bulk(unsigned int nr_pages, struct page **pages)
__free_page(pages[i]);
}

-static int tdx_alloc_pages_bulk(unsigned int nr_pages, struct page **pages)
+static int tdx_alloc_pages_bulk(unsigned int nr_pages, struct page **pages,
+ void *data)
{
unsigned int filled, done = 0;

@@ -326,7 +327,10 @@ void tdx_page_array_free(struct tdx_page_array *array)
EXPORT_SYMBOL_GPL(tdx_page_array_free);

static struct tdx_page_array *
-tdx_page_array_alloc(unsigned int nr_pages)
+tdx_page_array_alloc(unsigned int nr_pages,
+ int (*alloc_fn)(unsigned int nr_pages,
+ struct page **pages, void *data),
+ void *data)
{
struct tdx_page_array *array = NULL;
struct page **pages = NULL;
@@ -348,7 +352,7 @@ tdx_page_array_alloc(unsigned int nr_pages)
if (!pages)
goto out_free;

- ret = tdx_alloc_pages_bulk(nr_pages, pages);
+ ret = alloc_fn(nr_pages, pages, data);
if (ret)
goto out_free;

@@ -388,7 +392,7 @@ struct tdx_page_array *tdx_page_array_create(unsigned int nr_pages)
if (nr_pages > TDX_PAGE_ARRAY_MAX_NENTS)
return NULL;

- array = tdx_page_array_alloc(nr_pages);
+ array = tdx_page_array_alloc(nr_pages, tdx_alloc_pages_bulk, NULL);
if (!array)
return NULL;

@@ -521,6 +525,36 @@ int tdx_page_array_ctrl_release(struct tdx_page_array *array,
}
EXPORT_SYMBOL_GPL(tdx_page_array_ctrl_release);

+static int tdx_alloc_pages_contig(unsigned int nr_pages, struct page **pages,
+ void *data)
+{
+ struct page *page;
+ int i;
+
+ page = alloc_contig_pages(nr_pages, GFP_KERNEL, numa_mem_id(),
+ &node_online_map);
+ if (!page)
+ return -ENOMEM;
+
+ for (i = 0; i < nr_pages; i++)
+ pages[i] = page + i;
+
+ return 0;
+}
+
+/*
+ * For holding large number of contiguous pages, usually larger than
+ * TDX_PAGE_ARRAY_MAX_NENTS (512).
+ *
+ * Similar to tdx_page_array_alloc(), after allocating with this
+ * function, call tdx_page_array_populate() to populate the tdx_page_array.
+ */
+static __maybe_unused struct tdx_page_array *
+tdx_page_array_alloc_contig(unsigned int nr_pages)
+{
+ return tdx_page_array_alloc(nr_pages, tdx_alloc_pages_contig, NULL);
+}
+
#define HPA_LIST_INFO_FIRST_ENTRY GENMASK_U64(11, 3)
#define HPA_LIST_INFO_PFN GENMASK_U64(51, 12)
#define HPA_LIST_INFO_LAST_ENTRY GENMASK_U64(63, 55)
--
2.25.1