On Wed, May 06, 2026 at 01:44:53PM +0000, Anirudh Rayabharam (Microsoft) wrote: > The hypervisor's map GPA hypercall coalesces contiguous 2M-aligned > chunks into 1G mappings when alignment permits, so the driver can > support 1G hugepages by feeding them in as 2M chunks. Note that this > is the only way to make 1G mappings; there is no way to directly map > a 1G hugepage using the hypercall. > > Update mshv_chunk_stride() to: > > - Accept 2M-aligned tail pages of a larger folio. The previous > PageHead() check rejected every page after the head of a 1G > hugepage and fell back to 4K mappings for the remaining 1022 MB. > Replace it with a PFN alignment check so any 2M-aligned page of a > sufficiently large folio is acceptable. > > - Always emit a 2M (PMD_ORDER) stride for the huge-page case. The > hypercall has no 1G stride, so 1G folios are processed as a > sequence of 2M chunks. Folios whose order is neither PMD_ORDER nor > PUD_ORDER (e.g. mTHP) fall back to single-page stride; mapping > them as 2M would fail in the hypervisor anyway. > > Assisted-by: Copilot-CLI:claude-opus-4.7 > Signed-off-by: Anirudh Rayabharam (Microsoft) <[email protected]> > --- > Changes in v3: > - Fixed various corner cases reported by Sashiko. > - Link to v2: > https://lore.kernel.org/r/[email protected] > > Changes in v2:
LGTM, thanks. Acked-by: Stanislav Kinsburskii <[email protected]> > - Handled the case where we can have 2M aligned pages in the middle of a > 1G page > - Brought back the page order check but expanded it to include 1G > - Clamp stride to requested page count in mshv_region_process_chunk > - Link to v1: > https://lore.kernel.org/r/[email protected] > --- > drivers/hv/mshv_regions.c | 32 +++++++++++++++----------------- > 1 file changed, 15 insertions(+), 17 deletions(-) > > diff --git a/drivers/hv/mshv_regions.c b/drivers/hv/mshv_regions.c > index fdffd4f002f6..1756b733968c 100644 > --- a/drivers/hv/mshv_regions.c > +++ b/drivers/hv/mshv_regions.c > @@ -29,29 +29,28 @@ > * 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. > + * Return: Stride in pages. > */ > -static int mshv_chunk_stride(struct page *page, > - u64 gfn, u64 page_count) > +static unsigned int mshv_chunk_stride(struct page *page, u64 gfn, > + u64 page_count) > { > - unsigned int page_order; > + unsigned int page_order = folio_order(page_folio(page)); > > /* > * 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. > + * page must be compound, the page's PFN must itself be 2M-aligned > + * (so that a 2M-aligned tail page of a larger folio is acceptable), > + * and both gfn and page_count must be huge-page aligned. > */ > - if (!PageCompound(page) || !PageHead(page) || > + if (!PageCompound(page) || > + !IS_ALIGNED(page_to_pfn(page), PTRS_PER_PMD) || > !IS_ALIGNED(gfn, PTRS_PER_PMD) || > - !IS_ALIGNED(page_count, PTRS_PER_PMD)) > + !IS_ALIGNED(page_count, PTRS_PER_PMD) || > + (page_order != PMD_ORDER && page_order != PUD_ORDER)) > 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; > + /* Use 2M stride always i.e. process 1G folios as 2M chunks */ > + return 1 << PMD_ORDER; > } > > /** > @@ -86,15 +85,14 @@ static long mshv_region_process_chunk(struct > mshv_mem_region *region, > u64 gfn = region->start_gfn + page_offset; > u64 count; > struct page *page; > - int stride, ret; > + unsigned int stride; > + int ret; > > page = region->mreg_pages[page_offset]; > if (!page) > return -EINVAL; > > stride = mshv_chunk_stride(page, gfn, page_count); > - if (stride < 0) > - return stride; > > /* Start at stride since the first stride is validated */ > for (count = stride; count < page_count; count += stride) { > > --- > base-commit: cd9f2e7d6e5b1837ef40b96e300fa28b73ab5a77 > change-id: 20260416-huge_1g-e44461393c8f > > Best regards, > -- > Anirudh Rayabharam (Microsoft) <[email protected]> >
