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@xxxxxxxxxx>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Signed-off-by: Dongwon Kim <dongwon.kim@xxxxxxxxx>
---
drivers/dma-buf/udmabuf.c | 50 +++++++++++++++++++++++++++++++++------
1 file changed, 43 insertions(+), 7 deletions(-)
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index db732f71e59a..d509f0d60794 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 */
@@ -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_ERR(page)) {
- ret = PTR_ERR(page);
- goto err;
+ 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;
--
2.30.2
