Commit 16c243e9 authored by Vivek Kasireddy's avatar Vivek Kasireddy Committed by Gerd Hoffmann
Browse files

udmabuf: Add support for mapping hugepages (v4) 



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 and hugepage offsets are calculated correctly
when the range of subpage allocations cuts across multiple hugepages.

v3: Instead of repeatedly looking up the hugepage for each subpage,
only do it when the subpage allocation crosses over into a different
hugepage. (suggested by Gerd and DW)

v4: Fix the following warning identified by checkpatch:
CHECK:OPEN_ENDED_LINE: Lines should not end with a '('

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: default avatarVivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: default avatarDongwon Kim <dongwon.kim@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210609182915.592743-1-vivek.kasireddy@intel.com


[ kraxel: one more checkpatch format tweak ]
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 6eca310e

drivers/dma-buf/udmabuf.c

+43 −7
Original line number Diff line number Diff line
@@ -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  */
@@ -160,10 +161,13 @@ static long udmabuf_create(struct miscdevice *device, 
{

	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

	struct file *memfd = NULL;

	struct address_space *mapping = NULL;

	struct udmabuf *ubuf;

	struct dma_buf *buf;

	pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit;

	struct page *page;

	struct page *page, *hpage = NULL;

	pgoff_t subpgoff, maxsubpgs;

	struct hstate *hpstate;

	int seals, ret = -EINVAL;

	u32 i, flags;
@@ -194,7 +198,8 @@ static long udmabuf_create(struct miscdevice *device, 
		memfd = fget(list[i].memfd);

		if (!memfd)

			goto err;

		if (!shmem_mapping(file_inode(memfd)->i_mapping))

		mapping = file_inode(memfd)->i_mapping;

		if (!shmem_mapping(mapping) && !is_file_hugepages(memfd))

			goto err;

		seals = memfd_fcntl(memfd, F_GET_SEALS, 0);

		if (seals == -EINVAL)
@@ -205,17 +210,48 @@ 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_file_hugepages(memfd)) {

				if (!hpage) {

					hpage = find_get_page_flags(mapping, pgoff,

								    FGP_ACCESSED);

					if (IS_ERR(hpage)) {

						ret = PTR_ERR(hpage);

						goto err;

					}

				}

				page = hpage + subpgoff;

				get_page(page);

				subpgoff++;

				if (subpgoff == maxsubpgs) {

					put_page(hpage);

					hpage = NULL;

					subpgoff = 0;

					pgoff++;

				}

			} else {

				page = shmem_read_mapping_page(mapping,

							       pgoff + pgidx);

				if (IS_ERR(page)) {

					ret = PTR_ERR(page);

					goto err;

				}

			}

			ubuf->pages[pgbuf++] = page;

		}

		fput(memfd);

		memfd = NULL;

		if (hpage) {

			put_page(hpage);

			hpage = NULL;

		}

	}



	exp_info.ops  = &udmabuf_ops;