memfd: fix vhost-user-test on non-memfd capable host

On RHEL7, memfd is not supported, and vhost-user-test fails:
TEST: tests/vhost-user-test... (pid=10248)
  /x86_64/vhost-user/migrate:
  qemu-system-x86_64: -object memory-backend-memfd,id=mem,size=2M,: failed to create memfd
FAIL

There is a qemu_memfd_check() to prevent running memfd path, but it
also checks for fallback implementation. Let's specialize
qemu_memfd_check() to check memfd only, while qemu_memfd_alloc_check()
checks for the qemu_memfd_alloc() API.

Reported-by: Miroslav Rezanina <mrezanin@redhat.com>
Tested-by: Miroslav Rezanina <mrezanin@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180328121804.16203-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 250f886acb0ab617c24f9b81dcff2a55fba8e906..27c1ec5fe85a6cd149ae1aa3367f1d84db55f246 100644 (file)
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1223,7 +1223,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         if (!(hdev->features & (0x1ULL << VHOST_F_LOG_ALL))) {
             error_setg(&hdev->migration_blocker,
                        "Migration disabled: vhost lacks VHOST_F_LOG_ALL feature.");
-        } else if (vhost_dev_log_is_shared(hdev) && !qemu_memfd_check()) {
+        } else if (vhost_dev_log_is_shared(hdev) && !qemu_memfd_alloc_check()) {
             error_setg(&hdev->migration_blocker,
                        "Migration disabled: failed to allocate shared memory");
         }

diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index de10198ed660c473c81aee6a2b6ea0365e2b78f2..49e79634dadf70c00e770299d175c438208f3091 100644 (file)
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -18,6 +18,7 @@
 
 int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
                       uint64_t hugetlbsize, unsigned int seals, Error **errp);
+bool qemu_memfd_alloc_check(void);
 void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
                        int *fd, Error **errp);
 void qemu_memfd_free(void *ptr, size_t size, int fd);

diff --git a/util/memfd.c b/util/memfd.c
index 07d579ea7d9853a2e7b2a987f2ff390bde42bec2..b3ecbac19e9017e0aa4868da7837e7ec305a96e3 100644 (file)
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -173,7 +173,13 @@ enum {
     MEMFD_TODO
 };
 
-bool qemu_memfd_check(void)
+/**
+ * qemu_memfd_alloc_check():
+ *
+ * Check if qemu_memfd_alloc() can allocate, including using a
+ * fallback implementation when host doesn't support memfd.
+ */
+bool qemu_memfd_alloc_check(void)
 {
     static int memfd_check = MEMFD_TODO;
 
@@ -188,3 +194,29 @@ bool qemu_memfd_check(void)
 
     return memfd_check == MEMFD_OK;
 }
+
+/**
+ * qemu_memfd_check():
+ *
+ * Check if host supports memfd.
+ */
+bool qemu_memfd_check(void)
+{
+#ifdef CONFIG_LINUX
+    static int memfd_check = MEMFD_TODO;
+
+    if (memfd_check == MEMFD_TODO) {
+        int mfd = memfd_create("test", 0);
+        if (mfd >= 0) {
+            memfd_check = MEMFD_OK;
+            close(mfd);
+        } else {
+            memfd_check = MEMFD_KO;
+        }
+    }
+
+    return memfd_check == MEMFD_OK;
+#else
+    return false;
+#endif
+}