Commit 259add0d authored by Stanislav Kinsburskii's avatar Stanislav Kinsburskii Committed by Wei Liu
Browse files

mshv: Align huge page stride with guest mapping 



Ensure that a stride larger than 1 (huge page) is only used when page
points to a head of a huge page and both the guest frame number (gfn) and
the operation size (page_count) are aligned to the huge page size
(PTRS_PER_PMD). This matches the hypervisor requirement that map/unmap
operations for huge pages must be guest-aligned and cover a full huge page.

Add mshv_chunk_stride() to encapsulate this alignment and page-order
validation, and plumb a huge_page flag into the region chunk handlers.
This prevents issuing large-page map/unmap/share operations that the
hypervisor would reject due to misaligned guest mappings.

Fixes: abceb429 ("mshv: Fix huge page handling in memory region traversal")
Signed-off-by: default avatarStanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: default avatarNuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent 49f49d47

drivers/hv/mshv_regions.c

+62 −31
Original line number Diff line number Diff line
@@ -19,6 +19,41 @@ 


#define MSHV_MAP_FAULT_IN_PAGES				PTRS_PER_PMD



/**

 * mshv_chunk_stride - Compute stride for mapping guest memory

 * @page      : The page to check for huge page backing

 * @gfn       : Guest frame number for the mapping

 * @page_count: Total number of pages in the mapping

 *

 * Determines the appropriate stride (in pages) for mapping guest memory.

 * Uses huge page stride if the backing page is huge and the guest mapping

 * is properly aligned; otherwise falls back to single page stride.

 *

 * Return: Stride in pages, or -EINVAL if page order is unsupported.

 */

static int mshv_chunk_stride(struct page *page,

			     u64 gfn, u64 page_count)

{

	unsigned int page_order;



	/*

	 * Use single page stride by default. For huge page stride, the

	 * page must be compound and point to the head of the compound

	 * page, and both gfn and page_count must be huge-page aligned.

	 */

	if (!PageCompound(page) || !PageHead(page) ||

	    !IS_ALIGNED(gfn, PTRS_PER_PMD) ||

	    !IS_ALIGNED(page_count, PTRS_PER_PMD))

		return 1;



	page_order = folio_order(page_folio(page));

	/* The hypervisor only supports 2M huge page */

	if (page_order != PMD_ORDER)

		return -EINVAL;



	return 1 << page_order;

}



/**

 * mshv_region_process_chunk - Processes a contiguous chunk of memory pages

 *                             in a region.
@@ -45,25 +80,23 @@ static long mshv_region_process_chunk(struct mshv_mem_region *region, 
				      int (*handler)(struct mshv_mem_region *region,

						     u32 flags,

						     u64 page_offset,

						     u64 page_count))

						     u64 page_count,

						     bool huge_page))

{

	u64 count, stride;

	unsigned int page_order;

	u64 gfn = region->start_gfn + page_offset;

	u64 count;

	struct page *page;

	int ret;

	int stride, ret;



	page = region->pages[page_offset];

	if (!page)

		return -EINVAL;



	page_order = folio_order(page_folio(page));

	/* The hypervisor only supports 4K and 2M page sizes */

	if (page_order && page_order != PMD_ORDER)

		return -EINVAL;



	stride = 1 << page_order;

	stride = mshv_chunk_stride(page, gfn, page_count);

	if (stride < 0)

		return stride;



	/* Start at stride since the first page is validated */

	/* Start at stride since the first stride is validated */

	for (count = stride; count < page_count; count += stride) {

		page = region->pages[page_offset + count];
@@ -71,12 +104,13 @@ static long mshv_region_process_chunk(struct mshv_mem_region *region, 
		if (!page)

			break;



		/* Break if page size changes */

		if (page_order != folio_order(page_folio(page)))

		/* Break if stride size changes */

		if (stride != mshv_chunk_stride(page, gfn + count,

						page_count - count))

			break;

	}



	ret = handler(region, flags, page_offset, count);

	ret = handler(region, flags, page_offset, count, stride > 1);

	if (ret)

		return ret;
@@ -108,7 +142,8 @@ static int mshv_region_process_range(struct mshv_mem_region *region, 
				     int (*handler)(struct mshv_mem_region *region,

						    u32 flags,

						    u64 page_offset,

						    u64 page_count))

						    u64 page_count,

						    bool huge_page))

{

	long ret;
@@ -162,11 +197,10 @@ struct mshv_mem_region *mshv_region_create(u64 guest_pfn, u64 nr_pages, 


static int mshv_region_chunk_share(struct mshv_mem_region *region,

				   u32 flags,

				   u64 page_offset, u64 page_count)

				   u64 page_offset, u64 page_count,

				   bool huge_page)

{

	struct page *page = region->pages[page_offset];



	if (PageHuge(page) || PageTransCompound(page))

	if (huge_page)

		flags |= HV_MODIFY_SPA_PAGE_HOST_ACCESS_LARGE_PAGE;



	return hv_call_modify_spa_host_access(region->partition->pt_id,
@@ -188,11 +222,10 @@ int mshv_region_share(struct mshv_mem_region *region) 


static int mshv_region_chunk_unshare(struct mshv_mem_region *region,

				     u32 flags,

				     u64 page_offset, u64 page_count)

				     u64 page_offset, u64 page_count,

				     bool huge_page)

{

	struct page *page = region->pages[page_offset];



	if (PageHuge(page) || PageTransCompound(page))

	if (huge_page)

		flags |= HV_MODIFY_SPA_PAGE_HOST_ACCESS_LARGE_PAGE;



	return hv_call_modify_spa_host_access(region->partition->pt_id,
@@ -212,11 +245,10 @@ int mshv_region_unshare(struct mshv_mem_region *region) 


static int mshv_region_chunk_remap(struct mshv_mem_region *region,

				   u32 flags,

				   u64 page_offset, u64 page_count)

				   u64 page_offset, u64 page_count,

				   bool huge_page)

{

	struct page *page = region->pages[page_offset];



	if (PageHuge(page) || PageTransCompound(page))

	if (huge_page)

		flags |= HV_MAP_GPA_LARGE_PAGE;



	return hv_call_map_gpa_pages(region->partition->pt_id,
@@ -295,11 +327,10 @@ int mshv_region_pin(struct mshv_mem_region *region) 


static int mshv_region_chunk_unmap(struct mshv_mem_region *region,

				   u32 flags,

				   u64 page_offset, u64 page_count)

				   u64 page_offset, u64 page_count,

				   bool huge_page)

{

	struct page *page = region->pages[page_offset];



	if (PageHuge(page) || PageTransCompound(page))

	if (huge_page)

		flags |= HV_UNMAP_GPA_LARGE_PAGE;



	return hv_call_unmap_gpa_pages(region->partition->pt_id,