On Thu, Feb 14, 2019 at 11:10:04AM +0800, Stefan Hajnoczi wrote:
>Guests started with NVDIMMs larger than the underlying host file produce
>confusing errors inside the guest. This happens because the guest
>accesses pages beyond the end of the file.
>
>Check the pmem file size on startup and print a clear error message if
>the size is invalid.
>
>Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1669053
>Cc: Wei Yang <richardw.y...@linux.intel.com>
>Cc: Zhang Yi <yi.z.zh...@linux.intel.com>
>Cc: Eduardo Habkost <ehabk...@redhat.com>
>Cc: Igor Mammedov <imamm...@redhat.com>
>Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
>---
> include/qemu/osdep.h | 13 ++++++++++
> backends/hostmem-file.c | 23 ++++++++++++++++++
> util/oslib-posix.c | 53 +++++++++++++++++++++++++++++++++++++++++
> util/oslib-win32.c | 5 ++++
> 4 files changed, 94 insertions(+)
>
>diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
>index 840af09cb0..303d315c5d 100644
>--- a/include/qemu/osdep.h
>+++ b/include/qemu/osdep.h
>@@ -570,6 +570,19 @@ void qemu_set_tty_echo(int fd, bool echo);
> void os_mem_prealloc(int fd, char *area, size_t sz, int smp_cpus,
> Error **errp);
>
>+/**
>+ * qemu_get_pmem_size:
>+ * @filename: path to a pmem file
>+ * @errp: pointer to a NULL-initialized error object
>+ *
>+ * Determine the size of a persistent memory file. Besides supporting files
>on
>+ * DAX file systems, this function also supports Linux devdax character
>+ * devices.
>+ *
>+ * Returns: the size or 0 on failure
>+ */
>+uint64_t qemu_get_pmem_size(const char *filename, Error **errp);
>+
> /**
> * qemu_get_pid_name:
> * @pid: pid of a process
>diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
>index ce54788048..37ac6445d2 100644
>--- a/backends/hostmem-file.c
>+++ b/backends/hostmem-file.c
>@@ -56,6 +56,29 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error
>**errp)
> error_setg(errp, "mem-path property not set");
> return;
> }
>+
>+ /*
>+ * Verify pmem file size since starting a guest with an incorrect size
>+ * leads to confusing failures inside the guest.
>+ */
>+ if (fb->is_pmem) {
>+ Error *local_err = NULL;
>+ uint64_t size;
>+
>+ size = qemu_get_pmem_size(fb->mem_path, &local_err);
>+ if (!size) {
>+ error_propagate(errp, local_err);
>+ return;
>+ }
>+
>+ 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;
>+ }
>+ }
>+
> backend->force_prealloc = mem_prealloc;
> name = host_memory_backend_get_name(backend);
> memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
>diff --git a/util/oslib-posix.c b/util/oslib-posix.c
>index 37c5854b9c..10d90d1783 100644
>--- a/util/oslib-posix.c
>+++ b/util/oslib-posix.c
>@@ -500,6 +500,59 @@ void os_mem_prealloc(int fd, char *area, size_t memory,
>int smp_cpus,
> }
> }
>
>+uint64_t qemu_get_pmem_size(const char *filename, Error **errp)
>+{
>+ struct stat st;
>+
>+ if (stat(filename, &st) < 0) {
>+ error_setg(errp, "unable to stat pmem file \"%s\"", filename);
>+ return 0;
>+ }
>+
>+#if defined(__linux__)
>+ /* Special handling for devdax character devices */
>+ if (S_ISCHR(st.st_mode)) {
>+ char *subsystem_path = NULL;
>+ char *subsystem = NULL;
>+ char *size_path = NULL;
>+ char *size_str = NULL;
>+ uint64_t ret = 0;
>+
>+ 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) {
>+ error_setg(errp, "unable to read subsystem for pmem file \"%s\"",
>+ filename);
>+ goto devdax_err;
>+ }
>+
>+ if (!g_str_has_suffix(subsystem, "/dax")) {
>+ error_setg(errp, "pmem file \"%s\" is not a dax device",
>filename);
>+ goto devdax_err;
>+ }
>+
>+ 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)) {
>+ error_setg(errp, "unable to read size for pmem file \"%s\"",
>+ size_path);
>+ goto devdax_err;
>+ }
>+
>+ ret = g_ascii_strtoull(size_str, NULL, 0);
>+
>+devdax_err:
>+ g_free(size_str);
>+ g_free(size_path);
>+ g_free(subsystem);
>+ g_free(subsystem_path);
>+ return ret;
>+ }
>+#endif /* defined(__linux__) */
>+
>+ return st.st_size;
>+}
>
> char *qemu_get_pid_name(pid_t pid)
> {
>diff --git a/util/oslib-win32.c b/util/oslib-win32.c
>index b4c17f5dfa..bd633afab6 100644
>--- a/util/oslib-win32.c
>+++ b/util/oslib-win32.c
>@@ -560,6 +560,11 @@ void os_mem_prealloc(int fd, char *area, size_t memory,
>int smp_cpus,
> }
> }
>
>+uint64_t qemu_get_pmem_size(const char *filename, Error **errp)
>+{
>+ error_setg(errp, "pmem support not available");
>+ return 0;
>+}
After the cleanup from Igor, qemu_get_pmem_size() would be invoked only on
POSIX system.
Is it still necessary to define this on win32?
>
> char *qemu_get_pid_name(pid_t pid)
> {
>--
>2.20.1
--
Wei Yang
Help you, Help me
