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: abceb4297bf8 ("mshv: Fix huge page handling in memory region traversal")
Signed-off-by: Stanislav Kinsburskii <[email protected]>
---
drivers/hv/mshv_regions.c | 93 ++++++++++++++++++++++++++++++---------------
1 file changed, 62 insertions(+), 31 deletions(-)
diff --git a/drivers/hv/mshv_regions.c b/drivers/hv/mshv_regions.c
index 30bacba6aec3..adba3564d9f1 100644
--- a/drivers/hv/mshv_regions.c
+++ b/drivers/hv/mshv_regions.c
@@ -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,
