On 2026/03/02 15:03, 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.cindex 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(structvirtio_gpu_simple_resource *res)+static int virtio_gpu_create_udmabuf(structvirtio_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_IOVI 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(structvirtio_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 withudmabuf ");+ return VFIO_DMABUF_CREATE_GUEST_ERROR; } list->list[i].memfd = rb->fd; @@ -56,22 +60,30 @@ static void virtio_gpu_create_udmabuf(structvirtio_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: ioctlfailed");+ 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(structvirtio_gpu_simple_resource *res)+static bool virtio_gpu_remap_dmabuf(structvirtio_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(structvirtio_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, VivekRegards, 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;
