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[PATCH 2/2] libvhost-user: replace qemu/memfd.h usage


From: marcandre . lureau
Subject: [PATCH 2/2] libvhost-user: replace qemu/memfd.h usage
Date: Wed, 18 Nov 2020 12:09:02 +0400

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Undo the damage from commit 5f9ff1eff3 ("libvhost-user: Support tracking
inflight I/O in shared memory") which introduced glib dependency through
osdep.h inclusion.

libvhost-user.c tries to stay free from glib usage.

Use glibc memfd_create directly when available (assumed so when
MFD_ALLOW_SEALING is defined).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 contrib/libvhost-user/libvhost-user.c | 50 +++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 7 deletions(-)

diff --git a/contrib/libvhost-user/libvhost-user.c 
b/contrib/libvhost-user/libvhost-user.c
index 1c1cfbf1e7..805521859d 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -42,8 +42,6 @@
 #endif
 
 #include "qemu/atomic.h"
-#include "qemu/osdep.h"
-#include "qemu/memfd.h"
 
 #include "libvhost-user.h"
 
@@ -1615,11 +1613,45 @@ vu_inflight_queue_size(uint16_t queue_size)
            sizeof(uint16_t), INFLIGHT_ALIGNMENT);
 }
 
+#ifdef MFD_ALLOW_SEALING
+static void *
+memfd_alloc(const char *name, size_t size, unsigned int flags, int *fd)
+{
+    void *ptr;
+    int ret;
+
+    *fd = memfd_create(name, MFD_ALLOW_SEALING);
+    if (*fd < 0) {
+        return NULL;
+    }
+
+    ret = ftruncate(*fd, size);
+    if (ret < 0) {
+        close(*fd);
+        return NULL;
+    }
+
+    ret = fcntl(*fd, F_ADD_SEALS, F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL);
+    if (ret < 0) {
+        close(*fd);
+        return NULL;
+    }
+
+    ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, *fd, 0);
+    if (ptr == MAP_FAILED) {
+        close(*fd);
+        return NULL;
+    }
+
+    return ptr;
+}
+#endif
+
 static bool
 vu_get_inflight_fd(VuDev *dev, VhostUserMsg *vmsg)
 {
-    int fd;
-    void *addr;
+    int fd = -1;
+    void *addr = NULL;
     uint64_t mmap_size;
     uint16_t num_queues, queue_size;
 
@@ -1637,9 +1669,13 @@ vu_get_inflight_fd(VuDev *dev, VhostUserMsg *vmsg)
 
     mmap_size = vu_inflight_queue_size(queue_size) * num_queues;
 
-    addr = qemu_memfd_alloc("vhost-inflight", mmap_size,
-                            F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
-                            &fd, NULL);
+#ifdef MFD_ALLOW_SEALING
+    addr = memfd_alloc("vhost-inflight", mmap_size,
+                       F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL,
+                       &fd);
+#else
+    vu_panic(dev, "Not implemented: memfd support is missing");
+#endif
 
     if (!addr) {
         vu_panic(dev, "Failed to alloc vhost inflight area");
-- 
2.29.0




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