From 72d41eb4b8f923de91e8f06dc20aa86b0a9155fb Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Fri, 30 Aug 2019 10:30:56 +0100 Subject: memory: fetch pmem size in get_file_size() Neither stat(2) nor lseek(2) report the size of Linux devdax pmem character device nodes. Commit 314aec4a6e06844937f1677f6cba21981005f389 ("hostmem-file: reject invalid pmem file sizes") added code to hostmem-file.c to fetch the size from sysfs and compare against the user-provided size=NUM parameter: if (backend->size > size) { error_setg(errp, "size property %" PRIu64 " is larger than " "pmem file \"%s\" size %" PRIu64, backend->size, fb->mem_path, size); return; } It turns out that exec.c:qemu_ram_alloc_from_fd() already has an equivalent size check but it skips devdax pmem character devices because lseek(2) returns 0: if (file_size > 0 && file_size < size) { error_setg(errp, "backing store %s size 0x%" PRIx64 " does not match 'size' option 0x" RAM_ADDR_FMT, mem_path, file_size, size); return NULL; } This patch moves the devdax pmem file size code into get_file_size() so that we check the memory size in a single place: qemu_ram_alloc_from_fd(). This simplifies the code and makes it more general. This also fixes the problem that hostmem-file only checks the devdax pmem file size when the pmem=on parameter is given. An unchecked size=NUM parameter can lead to SIGBUS in QEMU so we must always fetch the file size for Linux devdax pmem character device nodes. Signed-off-by: Stefan Hajnoczi Message-Id: <20190830093056.12572-1-stefanha@redhat.com> Reviewed-by: Eduardo Habkost Signed-off-by: Paolo Bonzini --- exec.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) (limited to 'exec.c') diff --git a/exec.c b/exec.c index b9511be096..8b998974f8 100644 --- a/exec.c +++ b/exec.c @@ -1791,7 +1791,39 @@ long qemu_maxrampagesize(void) #ifdef CONFIG_POSIX static int64_t get_file_size(int fd) { - int64_t size = lseek(fd, 0, SEEK_END); + int64_t size; +#if defined(__linux__) + struct stat st; + + if (fstat(fd, &st) < 0) { + return -errno; + } + + /* Special handling for devdax character devices */ + if (S_ISCHR(st.st_mode)) { + g_autofree char *subsystem_path = NULL; + g_autofree char *subsystem = NULL; + + subsystem_path = g_strdup_printf("/sys/dev/char/%d:%d/subsystem", + major(st.st_rdev), minor(st.st_rdev)); + subsystem = g_file_read_link(subsystem_path, NULL); + + if (subsystem && g_str_has_suffix(subsystem, "/dax")) { + g_autofree char *size_path = NULL; + g_autofree char *size_str = NULL; + + size_path = g_strdup_printf("/sys/dev/char/%d:%d/size", + major(st.st_rdev), minor(st.st_rdev)); + + if (g_file_get_contents(size_path, &size_str, NULL, NULL)) { + return g_ascii_strtoll(size_str, NULL, 0); + } + } + } +#endif /* defined(__linux__) */ + + /* st.st_size may be zero for special files yet lseek(2) works */ + size = lseek(fd, 0, SEEK_END); if (size < 0) { return -errno; } -- cgit v1.2.3