Hi Stefan,
> > 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: Haozhong Zhang <haozhong.zh...@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 | 16 +++++++++++++ > util/oslib-posix.c | 53 +++++++++++++++++++++++++++++++++++++++++ > util/oslib-win32.c | 5 ++++ > 4 files changed, 87 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 ba601ce940..325ab4aad9 100644 > --- a/backends/hostmem-file.c > +++ b/backends/hostmem-file.c > @@ -46,6 +46,22 @@ file_backend_memory_alloc(HostMemoryBackend *backend, > Error **errp) > gchar *name; > #endif > > + /* > + * Verify pmem file size since starting a guest with an incorrect size > + * leads to confusing failures inside the guest. > + */ > + if (fb->is_pmem && fb->mem_path) { > + uint64_t size; > + > + size = qemu_get_pmem_size(fb->mem_path, NULL); > + if (size && backend->size > size) { > + error_setg(errp, "size property %" PRIu64 " is larger than " > + "pmem file \"%s\" size %" PRIu64, backend->size, > + fb->mem_path, size); > + return; > + } > + } > + > if (!backend->size) { > error_setg(errp, "can't create backend with size 0"); > return; > 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; > +} > > char *qemu_get_pid_name(pid_t pid) > { > -- > 2.20.1 This patch looks good to me. Reviewed-by: Pankaj Gupta <pagu...@redhat.com> Thanks, Pankaj
