vfio: improve noiommu check error handling

Kernels v4.4 and earlier does have vfio, but not
the noiommu mode, so the file does not exist.

Check and report errors on open/read in noiommu check.

Signed-off-by: Jonas Pfefferle <jpf@zurich.ibm.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c b/lib/librte_eal/linuxapp/eal/eal_vfio.c
index 5371ec2..e44ae4d 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
+++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
@@ -814,20 +814,33 @@ vfio_noiommu_dma_map(int __rte_unused vfio_container_fd)
 int
 rte_vfio_noiommu_is_enabled(void)
 {
-       int fd, ret, cnt __rte_unused;
+       int fd;
+       ssize_t cnt;
        char c;
 
-       ret = -1;
        fd = open(VFIO_NOIOMMU_MODE, O_RDONLY);
-       if (fd < 0)
-               return -1;
+       if (fd < 0) {
+               if (errno != ENOENT) {
+                       RTE_LOG(ERR, EAL, "  cannot open vfio noiommu file %i (%s)\n",
+                                       errno, strerror(errno));
+                       return -1;
+               }
+               /*
+                * else the file does not exists
+                * i.e. noiommu is not enabled
+                */
+               return 0;
+       }
 
        cnt = read(fd, &c, 1);
-       if (c == 'Y')
-               ret = 1;
-
        close(fd);
-       return ret;
+       if (cnt != 1) {
+               RTE_LOG(ERR, EAL, "  unable to read from vfio noiommu "
+                               "file %i (%s)\n", errno, strerror(errno));
+               return -1;
+       }
+
+       return c == 'Y';
 }
 
 #endif