If the VMM's (Qemu) memory backend is backed up by memfd + Hugepages (hugetlbfs and not THP), we have to first find the hugepage(s) where the Guest allocations are located and then extract the regular 4k sized subpages from them.
v2: Ensure that the subpage offsets are calculated correctly when the range of subpage allocations cuts across multiple hugepages.
Cc: Gerd Hoffmann kraxel@redhat.com Signed-off-by: Vivek Kasireddy vivek.kasireddy@intel.com --- drivers/dma-buf/udmabuf.c | 46 ++++++++++++++++++++++++++++++++------- 1 file changed, 38 insertions(+), 8 deletions(-)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index db732f71e59a..f053d12a1eb3 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -11,6 +11,7 @@ #include <linux/shmem_fs.h> #include <linux/slab.h> #include <linux/udmabuf.h> +#include <linux/hugetlb.h>
static const u32 list_limit = 1024; /* udmabuf_create_list->count limit */ static const size_t size_limit_mb = 64; /* total dmabuf size, in megabytes */ @@ -162,8 +163,10 @@ static long udmabuf_create(struct miscdevice *device, struct file *memfd = NULL; struct udmabuf *ubuf; struct dma_buf *buf; - pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit; - struct page *page; + pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit, subpgoff; + uint32_t maxsubpgs; + struct page *page, *hpage = NULL; + struct hstate *hpstate; int seals, ret = -EINVAL; u32 i, flags;
@@ -194,7 +197,8 @@ static long udmabuf_create(struct miscdevice *device, memfd = fget(list[i].memfd); if (!memfd) goto err; - if (!shmem_mapping(file_inode(memfd)->i_mapping)) + if (!shmem_mapping(file_inode(memfd)->i_mapping) && + !is_file_hugepages(memfd)) goto err; seals = memfd_fcntl(memfd, F_GET_SEALS, 0); if (seals == -EINVAL) @@ -205,12 +209,38 @@ static long udmabuf_create(struct miscdevice *device, goto err; pgoff = list[i].offset >> PAGE_SHIFT; pgcnt = list[i].size >> PAGE_SHIFT; + if (is_file_hugepages(memfd)) { + hpstate = hstate_file(memfd); + pgoff = list[i].offset >> huge_page_shift(hpstate); + subpgoff = (list[i].offset & + ~huge_page_mask(hpstate)) >> PAGE_SHIFT; + maxsubpgs = huge_page_size(hpstate) >> PAGE_SHIFT; + } for (pgidx = 0; pgidx < pgcnt; pgidx++) { - page = shmem_read_mapping_page( - file_inode(memfd)->i_mapping, pgoff + pgidx); - if (IS_ERR(page)) { - ret = PTR_ERR(page); - goto err; + if (is_file_hugepages(memfd)) { + hpage = find_get_page_flags( + file_inode(memfd)->i_mapping, + pgoff, FGP_ACCESSED); + if (IS_ERR(hpage)) { + ret = PTR_ERR(hpage); + goto err; + } + + page = hpage + (subpgoff % maxsubpgs); + get_page(page); + put_page(hpage); + + subpgoff++; + if (subpgoff % maxsubpgs == 0) + pgoff++; + } else { + page = shmem_read_mapping_page( + file_inode(memfd)->i_mapping, + pgoff + pgidx); + if (IS_ERR(page)) { + ret = PTR_ERR(page); + goto err; + } } ubuf->pages[pgbuf++] = page; }