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From 9d6d365abaea5e068f060b8a70d5b8fab43a9f7f Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Wed, 18 Sep 2019 15:10:07 +0100
Subject: [PATCH 3/4] memory: fetch pmem size in get_file_size()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <20190918151007.27973-3-stefanha@redhat.com>
Patchwork-id: 90762
O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH 2/2] memory: fetch pmem size in get_file_size()
Bugzilla: 1724008 1736788
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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 <stefanha@redhat.com>
Message-Id: <20190830093056.12572-1-stefanha@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 72d41eb4b8f923de91e8f06dc20aa86b0a9155fb)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
backends/hostmem-file.c | 22 --------------------
exec.c | 34 ++++++++++++++++++++++++++++++-
include/qemu/osdep.h | 13 ------------
util/oslib-posix.c | 54 -------------------------------------------------
util/oslib-win32.c | 6 ------
5 files changed, 33 insertions(+), 96 deletions(-)
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index ecc15e3..be64020 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -58,28 +58,6 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
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 (local_err) {
- error_propagate(errp, local_err);
- return;
- }
-
- 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;
- }
- }
-
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/exec.c b/exec.c
index 3e78de3..3c03edf 100644
--- a/exec.c
+++ b/exec.c
@@ -1813,7 +1813,39 @@ 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;
}
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index af2b91f..c7d242f 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -571,19 +571,6 @@ 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 fe0309c..d772da8 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -513,60 +513,6 @@ 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)
{
char *name = NULL;
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 9583fb4..c62cd43 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -562,12 +562,6 @@ 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)
{
/* XXX Implement me */
--
1.8.3.1
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