fix qemu exit on memory hotplug when allocation fails at prealloc time

When adding hostmem backend at runtime, QEMU might exit with error:
  "os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM"

It happens due to os_mem_prealloc() not handling errors gracefully.

Fix it by passing errp argument so that os_mem_prealloc() could
report error to callers and undo performed allocation when
os_mem_prealloc() fails.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1469008443-72059-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 14 insertions, 14 deletions

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 6d70d9a706..f2d4e9e592 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -318,7 +318,7 @@ static void sigbus_handler(int signal)
     siglongjmp(sigjump, 1);
 }
 
-void os_mem_prealloc(int fd, char *area, size_t memory)
+void os_mem_prealloc(int fd, char *area, size_t memory, Error **errp)
 {
     int ret;
     struct sigaction act, oldact;
@@ -330,8 +330,9 @@ void os_mem_prealloc(int fd, char *area, size_t memory)
 
     ret = sigaction(SIGBUS, &act, &oldact);
     if (ret) {
-        perror("os_mem_prealloc: failed to install signal handler");
-        exit(1);
+        error_setg_errno(errp, errno,
+            "os_mem_prealloc: failed to install signal handler");
+        return;
     }
 
     /* unblock SIGBUS */
@@ -340,9 +341,8 @@ void os_mem_prealloc(int fd, char *area, size_t memory)
     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 
     if (sigsetjmp(sigjump, 1)) {
-        fprintf(stderr, "os_mem_prealloc: Insufficient free host memory "
-                        "pages available to allocate guest RAM\n");
-        exit(1);
+        error_setg(errp, "os_mem_prealloc: Insufficient free host memory "
+            "pages available to allocate guest RAM\n");
     } else {
         int i;
         size_t hpagesize = qemu_fd_getpagesize(fd);
@@ -352,15 +352,15 @@ void os_mem_prealloc(int fd, char *area, size_t memory)
         for (i = 0; i < numpages; i++) {
             memset(area + (hpagesize * i), 0, 1);
         }
+    }
 
-        ret = sigaction(SIGBUS, &oldact, NULL);
-        if (ret) {
-            perror("os_mem_prealloc: failed to reinstall signal handler");
-            exit(1);
-        }
-
-        pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+    ret = sigaction(SIGBUS, &oldact, NULL);
+    if (ret) {
+        /* Terminate QEMU since it can't recover from error */
+        perror("os_mem_prealloc: failed to reinstall signal handler");
+        exit(1);
     }
+    pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 }
 
 
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 6debc2b8a6..4c1dcf1e66 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -539,7 +539,7 @@ int getpagesize(void)
     return system_info.dwPageSize;
 }
 
-void os_mem_prealloc(int fd, char *area, size_t memory)
+void os_mem_prealloc(int fd, char *area, size_t memory, Error **errp)
 {
     int i;
     size_t pagesize = getpagesize();