On 2026/03/03 16:10, Kasireddy, Vivek wrote:
Hi Akihiko,
Subject: Re: [PATCH v8 09/10] virtio-gpu-dmabuf: Improve error
handling with 'Error **' and err enum
On 2026/02/28 7:13, Vivek Kasireddy wrote:
Make the error handling more robust in virtio_gpu_init_udmabuf()
by introducing 'Error **' parameter to capture errors and using an
enum from VFIO to categorize Guest and Host errors. This allows
for better error reporting and handling of errors from
virtio_gpu_create_udmabuf() and virtio_gpu_remap_dmabuf().
Cc: Marc-André Lureau <[email protected]>
Cc: Alex Bennée <[email protected]>
Cc: Akihiko Odaki <[email protected]>
Cc: Dmitry Osipenko <[email protected]>
Cc: Alex Williamson <[email protected]>
Cc: Cédric Le Goater <[email protected]>
Signed-off-by: Vivek Kasireddy <[email protected]>
---
hw/display/virtio-gpu-dmabuf.c | 61 ++++++++++++++++++++++++-
------
---
1 file changed, 43 insertions(+), 18 deletions(-)
diff --git a/hw/display/virtio-gpu-dmabuf.c b/hw/display/virtio-gpu-
dmabuf.c
index 8d67ef7c2a..b2badfc1bd 100644
--- a/hw/display/virtio-gpu-dmabuf.c
+++ b/hw/display/virtio-gpu-dmabuf.c
@@ -18,6 +18,7 @@
#include "ui/console.h"
#include "hw/virtio/virtio-gpu.h"
#include "hw/virtio/virtio-gpu-pixman.h"
+#include "hw/vfio/vfio-device.h"
#include "trace.h"
#include "system/ramblock.h"
#include "system/hostmem.h"
@@ -27,16 +28,18 @@
#include "standard-headers/linux/udmabuf.h"
#include "standard-headers/drm/drm_fourcc.h"
-static void virtio_gpu_create_udmabuf(struct
virtio_gpu_simple_resource *res)
+static int virtio_gpu_create_udmabuf(struct
virtio_gpu_simple_resource *res,
+ Error **errp)
{
g_autofree struct udmabuf_create_list *list = NULL;
RAMBlock *rb;
ram_addr_t offset;
- int udmabuf, i;
+ int udmabuf, i, fd;
udmabuf = udmabuf_fd();
if (udmabuf < 0) {
- return;
+ error_setg(errp, "udmabuf device not available or enabled");
+ return VFIO_DMABUF_CREATE_HOST_ERROR;
I failed to point out one thing for naming of the enum. The name
should
express if the error is caused by invalid iov or something else. Then
virtio-gpu decides how to recover the error; it's virtio-gpu who knows
the iov is from the guest and decides to report a guest error, not
vfio.
Otherwise, it reports a host error.
So, it sounds like you are suggesting that there needs to be three
enum
values:
enum {
/* Guest is responsible for this error */
VFIO_DMABUF_CREATE_GUEST_ERROR = -1,
/* Guest is at fault as the IOVEC passed in is invalid */
VFIO_DMABUF_CREATE_INVALID_IOV_ERROR = -2,
/* Host is at fault for this error */
VFIO_DMABUF_CREATE_HOST_ERROR = -3,
}
vfio doesn't know if the guest or the host is responsible, so it cannot
make use of VFIO_DMABUF_CREATE_GUEST_ERROR and
VFIO_DMABUF_CREATE_HOST_ERROR.
Or, please let me know in detail what changes you would like to see.
A possible combination of values is as follows:
- VFIO_DMABUF_CREATE_ERR_UNSPEC
- VFIO_DMABUF_CREATE_ERR_INVALID_IOV
Just these two error types are needed? Should I completely drop
VFIO_DMABUF_CREATE_GUEST_ERROR and VFIO_DMABUF_CREATE_HOST_ERROR,
even for udmabuf errors?
Yes, that's what I meant.
Regards,
Akihiko Odaki
Thanks,
Vivek
I took the example of VIRTIO_GPU_RESP_ERR_UNSPEC and
VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER for naming.
}
list = g_malloc0(sizeof(struct udmabuf_create_list) +
@@ -45,7 +48,8 @@ static void virtio_gpu_create_udmabuf(struct
virtio_gpu_simple_resource *res)
for (i = 0; i < res->iov_cnt; i++) {
rb = qemu_ram_block_from_host(res->iov[i].iov_base, false,
&offset);
if (!rb || rb->fd < 0) {
- return;
+ error_setg(errp, "IOV memory address incompatible with
udmabuf ");
+ return VFIO_DMABUF_CREATE_GUEST_ERROR;
}
list->list[i].memfd = rb->fd;
@@ -56,22 +60,30 @@ static void
virtio_gpu_create_udmabuf(struct
virtio_gpu_simple_resource *res)
list->count = res->iov_cnt;
list->flags = UDMABUF_FLAGS_CLOEXEC;
- res->dmabuf_fd = ioctl(udmabuf, UDMABUF_CREATE_LIST, list);
- if (res->dmabuf_fd < 0) {
- warn_report("%s: UDMABUF_CREATE_LIST: %s", __func__,
- strerror(errno));
+ fd = ioctl(udmabuf, UDMABUF_CREATE_LIST, list);
+ if (fd < 0) {
+ error_setg_errno(errp, errno, "UDMABUF_CREATE_LIST: ioctl
failed");
+ if (errno == EINVAL || errno == EBADFD) {
+ return VFIO_DMABUF_CREATE_GUEST_ERROR;
+ }
+ return VFIO_DMABUF_CREATE_HOST_ERROR;
}
+ return fd;
}
-static void virtio_gpu_remap_dmabuf(struct
virtio_gpu_simple_resource *res)
+static bool virtio_gpu_remap_dmabuf(struct
virtio_gpu_simple_resource *res,
+ Error **errp)
{
- res->remapped = mmap(NULL, res->blob_size, PROT_READ,
- MAP_SHARED, res->dmabuf_fd, 0);
- if (res->remapped == MAP_FAILED) {
- warn_report("%s: dmabuf mmap failed: %s", __func__,
- strerror(errno));
+ void *map;
+
+ map = mmap(NULL, res->blob_size, PROT_READ, MAP_SHARED,
res-
dmabuf_fd, 0);
+ if (map == MAP_FAILED) {
+ error_setg_errno(errp, errno, "dmabuf mmap failed");
res->remapped = NULL;
+ return false;
}
+ res->remapped = map;
+ return true;
}
static void virtio_gpu_destroy_dmabuf(struct
virtio_gpu_simple_resource *res)
@@ -125,19 +137,32 @@ bool virtio_gpu_have_udmabuf(void)
void virtio_gpu_init_dmabuf(struct virtio_gpu_simple_resource
*res)
{
+ Error *local_err = NULL;
void *pdata = NULL;
+ int ret;
res->dmabuf_fd = -1;
if (res->iov_cnt == 1 &&
res->iov[0].iov_len < 4096) {
pdata = res->iov[0].iov_base;
} else {
- virtio_gpu_create_udmabuf(res);
- if (res->dmabuf_fd < 0) {
+ ret = virtio_gpu_create_udmabuf(res, &local_err);
+ if (ret < 0) {
+ error_prepend(&local_err, "Cannot create dmabuf: ");
This error_prepend() is redundant. The error messages
virtio_gpu_create_udmabuf() emits already suggests they are
problems
with DMA-BUF.
Ok, I'll drop the error_prepend().
Thanks,
Vivek
Regards,
Akihiko Odaki
+
+ if (ret == VFIO_DMABUF_CREATE_GUEST_ERROR) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "Cannot create dmabuf: incompatible
memory\n");
+ error_free(local_err);
+ return;
+ }
+ error_report_err(local_err);
return;
}
- virtio_gpu_remap_dmabuf(res);
- if (!res->remapped) {
+
+ res->dmabuf_fd = ret;
+ if (!virtio_gpu_remap_dmabuf(res, &local_err)) {
+ error_report_err(local_err);
return;
}
pdata = res->remapped;
