[PATCH v2] Report stringified errno in VFIO related errors

[Michal Privoznik <mprivozn@redhat.com>]

In a few places we report errno formatted as a negative integer.
This is not as user friendly as it can be. Use strerror() and/or
error_setg_errno() instead.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---

v1 posted here:

https://lists.nongnu.org/archive/html/qemu-devel/2020-02/msg03623.html

diff to v1:
 - Change error reporting in vfio_dma_unmap() too as I missed it in v1.

 hw/vfio/common.c    | 4 ++--
 util/vfio-helpers.c | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 5ca11488d6..0b3593b3c0 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -319,7 +319,7 @@ static int vfio_dma_unmap(VFIOContainer *container,
             unmap.size -= 1ULL << ctz64(container->pgsizes);
             continue;
         }
-        error_report("VFIO_UNMAP_DMA: %d", -errno);
+        error_report("VFIO_UNMAP_DMA failed: %s", strerror(errno));
         return -errno;
     }
 
@@ -352,7 +352,7 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
         return 0;
     }
 
-    error_report("VFIO_MAP_DMA: %d", -errno);
+    error_report("VFIO_MAP_DMA failed: %s", strerror(errno));
     return -errno;
 }
 
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index 813f7ec564..ddd9a96e76 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -545,7 +545,7 @@ static int qemu_vfio_do_mapping(QEMUVFIOState *s, void *host, size_t size,
     trace_qemu_vfio_do_mapping(s, host, size, iova);
 
     if (ioctl(s->container, VFIO_IOMMU_MAP_DMA, &dma_map)) {
-        error_report("VFIO_MAP_DMA: %d", -errno);
+        error_report("VFIO_MAP_DMA failed: %s", strerror(errno));
         return -errno;
     }
     return 0;
@@ -570,7 +570,7 @@ static void qemu_vfio_undo_mapping(QEMUVFIOState *s, IOVAMapping *mapping,
     assert(QEMU_IS_ALIGNED(mapping->size, qemu_real_host_page_size));
     assert(index >= 0 && index < s->nr_mappings);
     if (ioctl(s->container, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
-        error_setg(errp, "VFIO_UNMAP_DMA failed: %d", -errno);
+        error_setg_errno(errp, errno, "VFIO_UNMAP_DMA failed");
     }
     memmove(mapping, &s->mappings[index + 1],
             sizeof(s->mappings[0]) * (s->nr_mappings - index - 1));
@@ -669,7 +669,7 @@ int qemu_vfio_dma_reset_temporary(QEMUVFIOState *s)
     trace_qemu_vfio_dma_reset_temporary(s);
     qemu_mutex_lock(&s->lock);
     if (ioctl(s->container, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
-        error_report("VFIO_UNMAP_DMA: %d", -errno);
+        error_report("VFIO_UNMAP_DMA failed: %s", strerror(errno));
         qemu_mutex_unlock(&s->lock);
         return -errno;
     }
-- 
2.24.1