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From 1b9f228788eb2d7f50961241e28f7a9afadc62ab Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 21 Mar 2019 10:56:08 +0000
Subject: [PATCH 7/9] hostmem-file: reject invalid pmem file sizes
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <20190321105608.29960-2-stefanha@redhat.com>
Patchwork-id: 85081
O-Subject: [RHEL-AV-8.0.1 qemu-kvm PATCH 1/1] hostmem-file: reject invalid pmem file sizes
Bugzilla: 1669053
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Acked-by: Pankaj Gupta <pagupta@redhat.com>
RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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.yang@linux.intel.com>
Cc: Zhang Yi <yi.z.zhang@linux.intel.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20190214031004.32522-3-stefanha@redhat.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Pankaj Gupta <pagupta@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
(cherry picked from commit 314aec4a6e06844937f1677f6cba21981005f389)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
backends/hostmem-file.c | 23 +++++++++++++++++++++
include/qemu/osdep.h | 13 ++++++++++++
util/oslib-posix.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++
util/oslib-win32.c | 5 +++++
4 files changed, 94 insertions(+)
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 6630021..8d85d56 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -57,6 +57,29 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
#ifndef CONFIG_POSIX
error_setg(errp, "-mem-path not supported on this host");
#else
+
+ /*
+ * 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;
path = object_get_canonical_path(OBJECT(backend));
memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 3bf48bc..c68a85b 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -553,6 +553,19 @@ 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/util/oslib-posix.c b/util/oslib-posix.c
index 97b2f3b..b173fc0 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -496,6 +496,59 @@ 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 b4c17f5..bd633af 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)
{
--
1.8.3.1
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