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mshv: Align huge page stride with guest mapping

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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: abceb4297b ("mshv: Fix huge page handling in memory region traversal")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
This commit is contained in:
Stanislav Kinsburskii 2026-01-07 18:45:43 +00:00 committed by Wei Liu
parent 49f49d47af
commit 259add0d98
1 changed files with 62 additions and 31 deletions
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93
drivers/hv/mshv_regions.c
View File

@ -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 = mshv_chunk_stride(page, gfn, page_count);
if (stride < 0)
return stride;
stride = 1 << page_order;
/* 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,