[Qemu-devel] [PATCH v4 2/6] exec: improve error handling and reporting in file_ram_alloc() and gethugepagesize()

[Hu Tao]

This patch fixes two problems of memory-backend-file:

1. If user adds a memory-backend-file object using object_add command,
   specifying a non-existing directory for property mem-path, qemu
   will core dump with message:

     /nonexistingdir: No such file or directory
     Bad ram offset fffffffffffff000
     Aborted (core dumped)

   with this patch, qemu reports error message like:

     qemu-system-x86_64: -object 
memory-backend-file,mem-path=/nonexistingdir,id=mem-file0,size=128M:
     failed to stat file /nonexistingdir: No such file or directory

2. If user adds a memory-backend-file object using object_add command,
   specifying a size that is less than huge page size, qemu
   will core dump with message:

     Bad ram offset fffffffffffff000
     Aborted (core dumped)

   with this patch, qemu reports error message like:

     qemu-system-x86_64: -object 
memory-backend-file,mem-path=/hugepages,id=mem-file0,size=1M: memory
     size 0x100000 should be euqal or larger than huge page size 0x200000

Signed-off-by: Hu Tao <address@hidden>
---
 exec.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/exec.c b/exec.c
index 7e60a44..6512820 100644
--- a/exec.c
+++ b/exec.c
@@ -996,7 +996,7 @@ void qemu_mutex_unlock_ramlist(void)
 
 #define HUGETLBFS_MAGIC       0x958458f6
 
-static long gethugepagesize(const char *path)
+static long gethugepagesize(const char *path, Error **errp)
 {
     struct statfs fs;
     int ret;
@@ -1006,7 +1006,7 @@ static long gethugepagesize(const char *path)
     } while (ret != 0 && errno == EINTR);
 
     if (ret != 0) {
-        perror(path);
+        error_setg_errno(errp, errno, "failed to get size of file %s", path);
         return 0;
     }
 
@@ -1024,17 +1024,20 @@ static void *file_ram_alloc(RAMBlock *block,
     char *filename;
     char *sanitized_name;
     char *c;
-    void *area;
+    void *area = NULL;
     int fd;
-    unsigned long hpagesize;
+    uint64_t hpagesize;
 
-    hpagesize = gethugepagesize(path);
-    if (!hpagesize) {
+    hpagesize = gethugepagesize(path, errp);
+    if (errp && *errp) {
         goto error;
     }
 
     if (memory < hpagesize) {
-        return NULL;
+        error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be euqal to "
+                   "or larger than huge page size 0x%" PRIx64,
+                   memory, hpagesize);
+        goto error;
     }
 
     if (kvm_enabled() && !kvm_has_sync_mmu()) {
@@ -1094,8 +1097,8 @@ static void *file_ram_alloc(RAMBlock *block,
     return area;
 
 error:
-    if (mem_prealloc) {
-        exit(1);
+    if (area && area != MAP_FAILED) {
+        munmap(area, memory);
     }
     return NULL;
 }
-- 
1.9.3