search for: virtq_desc_f_indirect

...> clear currently. > > > > > > > > In the spec, there are below words: > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > """ > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > is reserved and is ignored by the device. > > > > """ > > > > > > > > So when device writes back an used descriptor in this case, > > > > device may not set the VIRTQ_DESC_F_WRITE flag as the...

...> clear currently. > > > > > > > > In the spec, there are below words: > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > """ > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > is reserved and is ignored by the device. > > > > """ > > > > > > > > So when device writes back an used descriptor in this case, > > > > device may not set the VIRTQ_DESC_F_WRITE flag as the...

...gt; > > > > In the spec, there are below words: > > > > > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > > > """ > > > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > > > is reserved and is ignored by the device. > > > > > > """ > > > > > > > > > > > > So when device writes back an used descriptor in this case, > > > > > > devi...

...nk something related to this in the spec isn't very > > clear currently. > > > > In the spec, there are below words: > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > """ > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > is reserved and is ignored by the device. > > """ > > > > So when device writes back an used descriptor in this case, > > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > > is reserved and should be ignored....

...nk something related to this in the spec isn't very > > clear currently. > > > > In the spec, there are below words: > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > """ > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > is reserved and is ignored by the device. > > """ > > > > So when device writes back an used descriptor in this case, > > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > > is reserved and should be ignored....

...t; > > > > > > > > In the spec, there are below words: > > > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > > """ > > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > > is reserved and is ignored by the device. > > > > > """ > > > > > > > > > > So when device writes back an used descriptor in this case, > > > > > device may not set the VIRTQ_...

...;re right! The BUG_ON() isn't right. I'll remove it. And I think something related to this in the spec isn't very clear currently. In the spec, there are below words: https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 """ In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE is reserved and is ignored by the device. """ So when device writes back an used descriptor in this case, device may not set the VIRTQ_DESC_F_WRITE flag as the flag is reserved and should be ignored. https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/...

...;re right! The BUG_ON() isn't right. I'll remove it. And I think something related to this in the spec isn't very clear currently. In the spec, there are below words: https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 """ In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE is reserved and is ignored by the device. """ So when device writes back an used descriptor in this case, device may not set the VIRTQ_DESC_F_WRITE flag as the flag is reserved and should be ignored. https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/...

...spec isn't very > > > clear currently. > > > > > > In the spec, there are below words: > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > """ > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > is reserved and is ignored by the device. > > > """ > > > > > > So when device writes back an used descriptor in this case, > > > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > > > is re...

...t. I'll remove it. > And I think something related to this in the spec isn't very > clear currently. > > In the spec, there are below words: > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > """ > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > is reserved and is ignored by the device. > """ > > So when device writes back an used descriptor in this case, > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > is reserved and should be ignored. > > https://github.com/oa...

...lit_desc(vq); >>> + ret = fetch_indirect_descs(vq, last, head); >> >> Note that this means we don't supported chained indirect descriptors which >> complies the spec but we support this in vhost_get_vq_desc(). > Well the spec says: > A driver MUST NOT set both VIRTQ_DESC_F_INDIRECT and VIRTQ_DESC_F_NEXT in flags. > > Did I miss anything? > No, but I meant current vhost_get_vq_desc() supports chained indirect descriptor. Not sure if there's an application that depends on this silently. Thanks

On 2020/6/2 ??9:05, Michael S. Tsirkin wrote: > The idea is to support multiple ring formats by converting > to a format-independent array of descriptors. > > This costs extra cycles, but we gain in ability > to fetch a batch of descriptors in one go, which > is good for code cache locality. > > When used, this causes a minor performance degradation, > it's been kept

On 2020/6/2 ??9:05, Michael S. Tsirkin wrote: > The idea is to support multiple ring formats by converting > to a format-independent array of descriptors. > > This costs extra cycles, but we gain in ability > to fetch a batch of descriptors in one go, which > is good for code cache locality. > > When used, this causes a minor performance degradation, > it's been kept

...t; > + pop_split_desc(vq); > > + ret = fetch_indirect_descs(vq, last, head); > > > Note that this means we don't supported chained indirect descriptors which > complies the spec but we support this in vhost_get_vq_desc(). Well the spec says: A driver MUST NOT set both VIRTQ_DESC_F_INDIRECT and VIRTQ_DESC_F_NEXT in flags. Did I miss anything? > We probably need either fail early or just support that. > > Thanks > > > > + if (unlikely(ret < 0)) { > > + if (ret != -EAGAIN) > > + vq_err(vq, "Failure detected " > > +...

Hello everyone, This RFC implements packed ring support for virtio driver. The code was tested with DPDK vhost (testpmd/vhost-PMD) implemented by Jens at http://dpdk.org/ml/archives/dev/2018-January/089417.html Minor changes are needed for the vhost code, e.g. to kick the guest. TODO: - Refinements and bug fixes; - Split into small patches; - Test indirect descriptor support; - Test/fix event

Hello everyone, This RFC implements packed ring support for virtio driver. The code was tested with DPDK vhost (testpmd/vhost-PMD) implemented by Jens at http://dpdk.org/ml/archives/dev/2018-January/089417.html Minor changes are needed for the vhost code, e.g. to kick the guest. TODO: - Refinements and bug fixes; - Split into small patches; - Test indirect descriptor support; - Test/fix event