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udmabuf: Add support for mapping hugepages (v4)

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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: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon 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: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Vivek Kasireddy 2021-06-09 11:29:15 -07:00 committed by Gerd Hoffmann
parent 6eca310e89
commit 16c243e99d
1 changed files with 43 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

50
drivers/dma-buf/udmabuf.c
View file

@ -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;