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authorMarkus Armbruster <armbru@redhat.com>2016-03-07 20:25:14 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2016-03-15 18:23:33 +0100
commite1fb6471999939539ecfb21b41cbbb24047fa4dc (patch)
tree134b243bb9217b2547700d5b105c6ad99d8ee633 /exec.c
parentfd97fd4408040a9a6dfaf2fdaeca1c566db6d0aa (diff)
downloadqemu-arm-e1fb6471999939539ecfb21b41cbbb24047fa4dc.tar.gz
exec: Fix memory allocation when memory path isn't on hugetlbfs
gethugepagesize() works reliably only when its argument is on hugetlbfs. When it's not, it returns the filesystem's "optimal transfer block size", which may or may not be the actual page size you'll get when you mmap(). If the value is too small or not a power of two, we fail qemu_ram_mmap()'s assertions. These were added in commit 794e8f3 (v2.5.0). The bug's impact before that is currently unknown. Seems fairly unlikely at least when the normal page size is 4KiB. Else, if the value is too large, we align more strictly than necessary. gethugepagesize() goes back to commit c902760 (v0.13). That commit clearly intended gethugepagesize() to be used on hugetlbfs only. Not only was it named accordingly, it also printed a warning when used on anything else. However, the commit neglected to spell out the restriction in user documentation of -mem-path. Commit bfc2a1a (v2.5.0) dropped the warning as bogus "because QEMU functions perfectly well with the path on a regular tmpfs filesystem". It sure does when you're sufficiently lucky. In my testing, I was lucky, too. Fix by switching to qemu_fd_getpagesize(). Rename the variable holding its result from hpagesize to page_size. Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <1457378754-21649-3-git-send-email-armbru@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'exec.c')
-rw-r--r--exec.c40
1 files changed, 7 insertions, 33 deletions
diff --git a/exec.c b/exec.c
index 3380836748..274b619f88 100644
--- a/exec.c
+++ b/exec.c
@@ -1228,27 +1228,6 @@ void qemu_mutex_unlock_ramlist(void)
}
#ifdef __linux__
-
-#include <sys/vfs.h>
-
-#define HUGETLBFS_MAGIC 0x958458f6
-
-static long gethugepagesize(int fd)
-{
- struct statfs fs;
- int ret;
-
- do {
- ret = fstatfs(fd, &fs);
- } while (ret != 0 && errno == EINTR);
-
- if (ret != 0) {
- return -1;
- }
-
- return fs.f_bsize;
-}
-
static void *file_ram_alloc(RAMBlock *block,
ram_addr_t memory,
const char *path,
@@ -1260,7 +1239,7 @@ static void *file_ram_alloc(RAMBlock *block,
char *c;
void *area;
int fd;
- int64_t hpagesize;
+ int64_t page_size;
if (kvm_enabled() && !kvm_has_sync_mmu()) {
error_setg(errp,
@@ -1315,22 +1294,17 @@ static void *file_ram_alloc(RAMBlock *block,
*/
}
- hpagesize = gethugepagesize(fd);
- if (hpagesize < 0) {
- error_setg_errno(errp, errno, "can't get page size for %s",
- path);
- goto error;
- }
- block->mr->align = hpagesize;
+ page_size = qemu_fd_getpagesize(fd);
+ block->mr->align = page_size;
- if (memory < hpagesize) {
+ if (memory < page_size) {
error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
"or larger than page size 0x%" PRIx64,
- memory, hpagesize);
+ memory, page_size);
goto error;
}
- memory = ROUND_UP(memory, hpagesize);
+ memory = ROUND_UP(memory, page_size);
/*
* ftruncate is not supported by hugetlbfs in older
@@ -1342,7 +1316,7 @@ static void *file_ram_alloc(RAMBlock *block,
perror("ftruncate");
}
- area = qemu_ram_mmap(fd, memory, hpagesize, block->flags & RAM_SHARED);
+ area = qemu_ram_mmap(fd, memory, page_size, block->flags & RAM_SHARED);
if (area == MAP_FAILED) {
error_setg_errno(errp, errno,
"unable to map backing store for guest RAM");