[RFC v3 0/5] virtio: support packed ring

[RFC v3 0/5] virtio: support packed ring

[Tiwei Bie]

Hello everyone,

This RFC implements packed ring support in virtio driver.

Some simple functional tests have been done with Jason's
packed ring implementation in vhost:

https://lkml.org/lkml/2018/4/23/12

Both of ping and netperf worked as expected (with EVENT_IDX
disabled). But there are below known issues:

1. Reloading the guest driver will break the Tx/Rx;
2. Zeroing the flags when detaching a used desc will
   break the guest -> host path.

Some simple functional tests have also been done with
Wei's packed ring implementation in QEMU:

http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html

Both of ping and netperf worked as expected (with EVENT_IDX
disabled). Reloading the guest driver also worked as expected.

TODO:
- Refinements (for code and commit log) and bug fixes;
- Discuss/fix/test EVENT_IDX support;
- Test devices other than net;

RFC v2 -> RFC v3:
- Split into small patches (Jason);
- Add helper virtqueue_use_indirect() (Jason);
- Just set id for the last descriptor of a list (Jason);
- Calculate the prev in virtqueue_add_packed() (Jason);
- Fix/improve desc suppression code (Jason/MST);
- Refine the code layout for XXX_split/packed and wrappers (MST);
- Fix the comments and API in uapi (MST);
- Remove the BUG_ON() for indirect (Jason);
- Some other refinements and bug fixes;

RFC v1 -> RFC v2:
- Add indirect descriptor support - compile test only;
- Add event suppression supprt - compile test only;
- Move vring_packed_init() out of uapi (Jason, MST);
- Merge two loops into one in virtqueue_add_packed() (Jason);
- Split vring_unmap_one() for packed ring and split ring (Jason);
- Avoid using '%' operator (Jason);
- Rename free_head -> next_avail_idx (Jason);
- Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
- Some other refinements and bug fixes;

Thanks!

Tiwei Bie (5):
  virtio: add packed ring definitions
  virtio_ring: support creating packed ring
  virtio_ring: add packed ring support
  virtio_ring: add event idx support in packed ring
  virtio_ring: enable packed ring

 drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
 include/linux/virtio_ring.h        |    8 +-
 include/uapi/linux/virtio_config.h |   12 +-
 include/uapi/linux/virtio_ring.h   |   36 +
 4 files changed, 1049 insertions(+), 278 deletions(-)

-- 
2.11.0

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月25日 13:15, Tiwei Bie wrote:
> Hello everyone,
>
> This RFC implements packed ring support in virtio driver.
>
> Some simple functional tests have been done with Jason's
> packed ring implementation in vhost:
>
> https://lkml.org/lkml/2018/4/23/12
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). But there are below known issues:
>
> 1. Reloading the guest driver will break the Tx/Rx;

It looks like the reason is we don't sync wrap counter information 
between host and qemu through VHOST_SET/GET_VRING_BASE. And both vhost 
and qemu need to do this through encoding warp counters to higher bits 
of vhost_vring_state.num,

Thanks

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月25日 13:15, Tiwei Bie wrote:
> Hello everyone,
>
> This RFC implements packed ring support in virtio driver.
>
> Some simple functional tests have been done with Jason's
> packed ring implementation in vhost:
>
> https://lkml.org/lkml/2018/4/23/12
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). But there are below known issues:
>
> 1. Reloading the guest driver will break the Tx/Rx;

It looks like the reason is we don't sync wrap counter information 
between host and qemu through VHOST_SET/GET_VRING_BASE. And both vhost 
and qemu need to do this through encoding warp counters to higher bits 
of vhost_vring_state.num,

Thanks
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Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月27日 17:12, Tiwei Bie wrote:
> On Fri, Apr 27, 2018 at 02:17:51PM +0800, Jason Wang wrote:
>> On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
>>> On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
>>>> On 2018年04月25日 13:15, Tiwei Bie wrote:
>>>>> Hello everyone,
>>>>>
>>>>> This RFC implements packed ring support in virtio driver.
>>>>>
>>>>> Some simple functional tests have been done with Jason's
>>>>> packed ring implementation in vhost:
>>>>>
>>>>> https://lkml.org/lkml/2018/4/23/12
>>>>>
>>>>> Both of ping and netperf worked as expected (with EVENT_IDX
>>>>> disabled). But there are below known issues:
>>>>>
>>>>> 1. Reloading the guest driver will break the Tx/Rx;
>>>> Will have a look at this issue.
>>>>
>>>>> 2. Zeroing the flags when detaching a used desc will
>>>>>       break the guest -> host path.
>>>> I still think zeroing flags is unnecessary or even a bug. At host, I track
>>>> last observed avail wrap counter and detect avail like (what is suggested in
>>>> the example code in the spec):
>>>>
>>>> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
>>>> {
>>>>          bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
>>>>
>>>>          return avail == vq->avail_wrap_counter;
>>>> }
>>>>
>>>> So zeroing wrap can not work with this obviously.
>>>>
>>>> Thanks
>>> I agree. I think what one should do is flip the available bit.
>>>
>> But is this flipping a must?
>>
>> Thanks
> Yeah, that's my question too. It seems to be a requirement
> for driver that, the only change to the desc status that a
> driver can do during running is to mark the desc as avail,
> and any other changes to the desc status are not allowed.
> Similarly, the device can only mark the desc as used, and
> any other changes to the desc status are also not allowed.
> So the question is, are there such requirements?

Looks not, but I think we need clarify this in the spec.

Thanks

>
> Based on below contents in the spec:
>
> """
> Thus VIRTQ_DESC_F_AVAIL and VIRTQ_DESC_F_USED bits are different
> for an available descriptor and equal for a used descriptor.
>
> Note that this observation is mostly useful for sanity-checking
> as these are necessary but not sufficient conditions
> """
>
> It seems that, it's necessary for devices to check whether
> the AVAIL bit and USED bit are different.
>
> Best regards,
> Tiwei Bie

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月27日 17:12, Tiwei Bie wrote:
> On Fri, Apr 27, 2018 at 02:17:51PM +0800, Jason Wang wrote:
>> On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
>>> On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
>>>> On 2018年04月25日 13:15, Tiwei Bie wrote:
>>>>> Hello everyone,
>>>>>
>>>>> This RFC implements packed ring support in virtio driver.
>>>>>
>>>>> Some simple functional tests have been done with Jason's
>>>>> packed ring implementation in vhost:
>>>>>
>>>>> https://lkml.org/lkml/2018/4/23/12
>>>>>
>>>>> Both of ping and netperf worked as expected (with EVENT_IDX
>>>>> disabled). But there are below known issues:
>>>>>
>>>>> 1. Reloading the guest driver will break the Tx/Rx;
>>>> Will have a look at this issue.
>>>>
>>>>> 2. Zeroing the flags when detaching a used desc will
>>>>>       break the guest -> host path.
>>>> I still think zeroing flags is unnecessary or even a bug. At host, I track
>>>> last observed avail wrap counter and detect avail like (what is suggested in
>>>> the example code in the spec):
>>>>
>>>> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
>>>> {
>>>>          bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
>>>>
>>>>          return avail == vq->avail_wrap_counter;
>>>> }
>>>>
>>>> So zeroing wrap can not work with this obviously.
>>>>
>>>> Thanks
>>> I agree. I think what one should do is flip the available bit.
>>>
>> But is this flipping a must?
>>
>> Thanks
> Yeah, that's my question too. It seems to be a requirement
> for driver that, the only change to the desc status that a
> driver can do during running is to mark the desc as avail,
> and any other changes to the desc status are not allowed.
> Similarly, the device can only mark the desc as used, and
> any other changes to the desc status are also not allowed.
> So the question is, are there such requirements?

Looks not, but I think we need clarify this in the spec.

Thanks

>
> Based on below contents in the spec:
>
> """
> Thus VIRTQ_DESC_F_AVAIL and VIRTQ_DESC_F_USED bits are different
> for an available descriptor and equal for a used descriptor.
>
> Note that this observation is mostly useful for sanity-checking
> as these are necessary but not sufficient conditions
> """
>
> It seems that, it's necessary for devices to check whether
> the AVAIL bit and USED bit are different.
>
> Best regards,
> Tiwei Bie

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Re: [RFC v3 0/5] virtio: support packed ring

[Tiwei Bie]

On Fri, Apr 27, 2018 at 02:17:51PM +0800, Jason Wang wrote:
> On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
> > On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
> > > On 2018年04月25日 13:15, Tiwei Bie wrote:
> > > > Hello everyone,
> > > > 
> > > > This RFC implements packed ring support in virtio driver.
> > > > 
> > > > Some simple functional tests have been done with Jason's
> > > > packed ring implementation in vhost:
> > > > 
> > > > https://lkml.org/lkml/2018/4/23/12
> > > > 
> > > > Both of ping and netperf worked as expected (with EVENT_IDX
> > > > disabled). But there are below known issues:
> > > > 
> > > > 1. Reloading the guest driver will break the Tx/Rx;
> > > Will have a look at this issue.
> > > 
> > > > 2. Zeroing the flags when detaching a used desc will
> > > >      break the guest -> host path.
> > > I still think zeroing flags is unnecessary or even a bug. At host, I track
> > > last observed avail wrap counter and detect avail like (what is suggested in
> > > the example code in the spec):
> > > 
> > > static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
> > > {
> > >         bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
> > > 
> > >         return avail == vq->avail_wrap_counter;
> > > }
> > > 
> > > So zeroing wrap can not work with this obviously.
> > > 
> > > Thanks
> > I agree. I think what one should do is flip the available bit.
> > 
> 
> But is this flipping a must?
> 
> Thanks

Yeah, that's my question too. It seems to be a requirement
for driver that, the only change to the desc status that a
driver can do during running is to mark the desc as avail,
and any other changes to the desc status are not allowed.
Similarly, the device can only mark the desc as used, and
any other changes to the desc status are also not allowed.
So the question is, are there such requirements?

Based on below contents in the spec:

"""
Thus VIRTQ_DESC_F_AVAIL and VIRTQ_DESC_F_USED bits are different
for an available descriptor and equal for a used descriptor.

Note that this observation is mostly useful for sanity-checking
as these are necessary but not sufficient conditions
"""

It seems that, it's necessary for devices to check whether
the AVAIL bit and USED bit are different.

Best regards,
Tiwei Bie

Re: [RFC v3 0/5] virtio: support packed ring

[Tiwei Bie]

On Fri, Apr 27, 2018 at 02:17:51PM +0800, Jason Wang wrote:
> On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
> > On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
> > > On 2018年04月25日 13:15, Tiwei Bie wrote:
> > > > Hello everyone,
> > > > 
> > > > This RFC implements packed ring support in virtio driver.
> > > > 
> > > > Some simple functional tests have been done with Jason's
> > > > packed ring implementation in vhost:
> > > > 
> > > > https://lkml.org/lkml/2018/4/23/12
> > > > 
> > > > Both of ping and netperf worked as expected (with EVENT_IDX
> > > > disabled). But there are below known issues:
> > > > 
> > > > 1. Reloading the guest driver will break the Tx/Rx;
> > > Will have a look at this issue.
> > > 
> > > > 2. Zeroing the flags when detaching a used desc will
> > > >      break the guest -> host path.
> > > I still think zeroing flags is unnecessary or even a bug. At host, I track
> > > last observed avail wrap counter and detect avail like (what is suggested in
> > > the example code in the spec):
> > > 
> > > static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
> > > {
> > >         bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
> > > 
> > >         return avail == vq->avail_wrap_counter;
> > > }
> > > 
> > > So zeroing wrap can not work with this obviously.
> > > 
> > > Thanks
> > I agree. I think what one should do is flip the available bit.
> > 
> 
> But is this flipping a must?
> 
> Thanks

Yeah, that's my question too. It seems to be a requirement
for driver that, the only change to the desc status that a
driver can do during running is to mark the desc as avail,
and any other changes to the desc status are not allowed.
Similarly, the device can only mark the desc as used, and
any other changes to the desc status are also not allowed.
So the question is, are there such requirements?

Based on below contents in the spec:

"""
Thus VIRTQ_DESC_F_AVAIL and VIRTQ_DESC_F_USED bits are different
for an available descriptor and equal for a used descriptor.

Note that this observation is mostly useful for sanity-checking
as these are necessary but not sufficient conditions
"""

It seems that, it's necessary for devices to check whether
the AVAIL bit and USED bit are different.

Best regards,
Tiwei Bie
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Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
> On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
>> On 2018年04月25日 13:15, Tiwei Bie wrote:
>>> Hello everyone,
>>>
>>> This RFC implements packed ring support in virtio driver.
>>>
>>> Some simple functional tests have been done with Jason's
>>> packed ring implementation in vhost:
>>>
>>> https://lkml.org/lkml/2018/4/23/12
>>>
>>> Both of ping and netperf worked as expected (with EVENT_IDX
>>> disabled). But there are below known issues:
>>>
>>> 1. Reloading the guest driver will break the Tx/Rx;
>> Will have a look at this issue.
>>
>>> 2. Zeroing the flags when detaching a used desc will
>>>      break the guest -> host path.
>> I still think zeroing flags is unnecessary or even a bug. At host, I track
>> last observed avail wrap counter and detect avail like (what is suggested in
>> the example code in the spec):
>>
>> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
>> {
>>         bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
>>
>>         return avail == vq->avail_wrap_counter;
>> }
>>
>> So zeroing wrap can not work with this obviously.
>>
>> Thanks
> I agree. I think what one should do is flip the available bit.
>

But is this flipping a must?

Thanks

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月27日 12:18, Michael S. Tsirkin wrote:
> On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
>> On 2018年04月25日 13:15, Tiwei Bie wrote:
>>> Hello everyone,
>>>
>>> This RFC implements packed ring support in virtio driver.
>>>
>>> Some simple functional tests have been done with Jason's
>>> packed ring implementation in vhost:
>>>
>>> https://lkml.org/lkml/2018/4/23/12
>>>
>>> Both of ping and netperf worked as expected (with EVENT_IDX
>>> disabled). But there are below known issues:
>>>
>>> 1. Reloading the guest driver will break the Tx/Rx;
>> Will have a look at this issue.
>>
>>> 2. Zeroing the flags when detaching a used desc will
>>>      break the guest -> host path.
>> I still think zeroing flags is unnecessary or even a bug. At host, I track
>> last observed avail wrap counter and detect avail like (what is suggested in
>> the example code in the spec):
>>
>> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
>> {
>>         bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
>>
>>         return avail == vq->avail_wrap_counter;
>> }
>>
>> So zeroing wrap can not work with this obviously.
>>
>> Thanks
> I agree. I think what one should do is flip the available bit.
>

But is this flipping a must?

Thanks
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
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Re: [RFC v3 0/5] virtio: support packed ring

[Michael S. Tsirkin]

On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
> 
> 
> On 2018年04月25日 13:15, Tiwei Bie wrote:
> > Hello everyone,
> > 
> > This RFC implements packed ring support in virtio driver.
> > 
> > Some simple functional tests have been done with Jason's
> > packed ring implementation in vhost:
> > 
> > https://lkml.org/lkml/2018/4/23/12
> > 
> > Both of ping and netperf worked as expected (with EVENT_IDX
> > disabled). But there are below known issues:
> > 
> > 1. Reloading the guest driver will break the Tx/Rx;
> 
> Will have a look at this issue.
> 
> > 2. Zeroing the flags when detaching a used desc will
> >     break the guest -> host path.
> 
> I still think zeroing flags is unnecessary or even a bug. At host, I track
> last observed avail wrap counter and detect avail like (what is suggested in
> the example code in the spec):
> 
> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
> {
>        bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
> 
>        return avail == vq->avail_wrap_counter;
> }
> 
> So zeroing wrap can not work with this obviously.
> 
> Thanks

I agree. I think what one should do is flip the available bit.

> > 
> > Some simple functional tests have also been done with
> > Wei's packed ring implementation in QEMU:
> > 
> > http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html
> > 
> > Both of ping and netperf worked as expected (with EVENT_IDX
> > disabled). Reloading the guest driver also worked as expected.
> > 
> > TODO:
> > - Refinements (for code and commit log) and bug fixes;
> > - Discuss/fix/test EVENT_IDX support;
> > - Test devices other than net;
> > 
> > RFC v2 -> RFC v3:
> > - Split into small patches (Jason);
> > - Add helper virtqueue_use_indirect() (Jason);
> > - Just set id for the last descriptor of a list (Jason);
> > - Calculate the prev in virtqueue_add_packed() (Jason);
> > - Fix/improve desc suppression code (Jason/MST);
> > - Refine the code layout for XXX_split/packed and wrappers (MST);
> > - Fix the comments and API in uapi (MST);
> > - Remove the BUG_ON() for indirect (Jason);
> > - Some other refinements and bug fixes;
> > 
> > RFC v1 -> RFC v2:
> > - Add indirect descriptor support - compile test only;
> > - Add event suppression supprt - compile test only;
> > - Move vring_packed_init() out of uapi (Jason, MST);
> > - Merge two loops into one in virtqueue_add_packed() (Jason);
> > - Split vring_unmap_one() for packed ring and split ring (Jason);
> > - Avoid using '%' operator (Jason);
> > - Rename free_head -> next_avail_idx (Jason);
> > - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
> > - Some other refinements and bug fixes;
> > 
> > Thanks!
> > 
> > Tiwei Bie (5):
> >    virtio: add packed ring definitions
> >    virtio_ring: support creating packed ring
> >    virtio_ring: add packed ring support
> >    virtio_ring: add event idx support in packed ring
> >    virtio_ring: enable packed ring
> > 
> >   drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
> >   include/linux/virtio_ring.h        |    8 +-
> >   include/uapi/linux/virtio_config.h |   12 +-
> >   include/uapi/linux/virtio_ring.h   |   36 +
> >   4 files changed, 1049 insertions(+), 278 deletions(-)
> > 

Re: [RFC v3 0/5] virtio: support packed ring

[Michael S. Tsirkin]

On Fri, Apr 27, 2018 at 11:56:05AM +0800, Jason Wang wrote:
> 
> 
> On 2018年04月25日 13:15, Tiwei Bie wrote:
> > Hello everyone,
> > 
> > This RFC implements packed ring support in virtio driver.
> > 
> > Some simple functional tests have been done with Jason's
> > packed ring implementation in vhost:
> > 
> > https://lkml.org/lkml/2018/4/23/12
> > 
> > Both of ping and netperf worked as expected (with EVENT_IDX
> > disabled). But there are below known issues:
> > 
> > 1. Reloading the guest driver will break the Tx/Rx;
> 
> Will have a look at this issue.
> 
> > 2. Zeroing the flags when detaching a used desc will
> >     break the guest -> host path.
> 
> I still think zeroing flags is unnecessary or even a bug. At host, I track
> last observed avail wrap counter and detect avail like (what is suggested in
> the example code in the spec):
> 
> static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
> {
>        bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);
> 
>        return avail == vq->avail_wrap_counter;
> }
> 
> So zeroing wrap can not work with this obviously.
> 
> Thanks

I agree. I think what one should do is flip the available bit.

> > 
> > Some simple functional tests have also been done with
> > Wei's packed ring implementation in QEMU:
> > 
> > http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html
> > 
> > Both of ping and netperf worked as expected (with EVENT_IDX
> > disabled). Reloading the guest driver also worked as expected.
> > 
> > TODO:
> > - Refinements (for code and commit log) and bug fixes;
> > - Discuss/fix/test EVENT_IDX support;
> > - Test devices other than net;
> > 
> > RFC v2 -> RFC v3:
> > - Split into small patches (Jason);
> > - Add helper virtqueue_use_indirect() (Jason);
> > - Just set id for the last descriptor of a list (Jason);
> > - Calculate the prev in virtqueue_add_packed() (Jason);
> > - Fix/improve desc suppression code (Jason/MST);
> > - Refine the code layout for XXX_split/packed and wrappers (MST);
> > - Fix the comments and API in uapi (MST);
> > - Remove the BUG_ON() for indirect (Jason);
> > - Some other refinements and bug fixes;
> > 
> > RFC v1 -> RFC v2:
> > - Add indirect descriptor support - compile test only;
> > - Add event suppression supprt - compile test only;
> > - Move vring_packed_init() out of uapi (Jason, MST);
> > - Merge two loops into one in virtqueue_add_packed() (Jason);
> > - Split vring_unmap_one() for packed ring and split ring (Jason);
> > - Avoid using '%' operator (Jason);
> > - Rename free_head -> next_avail_idx (Jason);
> > - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
> > - Some other refinements and bug fixes;
> > 
> > Thanks!
> > 
> > Tiwei Bie (5):
> >    virtio: add packed ring definitions
> >    virtio_ring: support creating packed ring
> >    virtio_ring: add packed ring support
> >    virtio_ring: add event idx support in packed ring
> >    virtio_ring: enable packed ring
> > 
> >   drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
> >   include/linux/virtio_ring.h        |    8 +-
> >   include/uapi/linux/virtio_config.h |   12 +-
> >   include/uapi/linux/virtio_ring.h   |   36 +
> >   4 files changed, 1049 insertions(+), 278 deletions(-)
> > 
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Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月25日 13:15, Tiwei Bie wrote:
> Hello everyone,
>
> This RFC implements packed ring support in virtio driver.
>
> Some simple functional tests have been done with Jason's
> packed ring implementation in vhost:
>
> https://lkml.org/lkml/2018/4/23/12
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). But there are below known issues:
>
> 1. Reloading the guest driver will break the Tx/Rx;

Will have a look at this issue.

> 2. Zeroing the flags when detaching a used desc will
>     break the guest -> host path.

I still think zeroing flags is unnecessary or even a bug. At host, I 
track last observed avail wrap counter and detect avail like (what is 
suggested in the example code in the spec):

static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
{
        bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);

        return avail == vq->avail_wrap_counter;
}

So zeroing wrap can not work with this obviously.

Thanks

>
> Some simple functional tests have also been done with
> Wei's packed ring implementation in QEMU:
>
> http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). Reloading the guest driver also worked as expected.
>
> TODO:
> - Refinements (for code and commit log) and bug fixes;
> - Discuss/fix/test EVENT_IDX support;
> - Test devices other than net;
>
> RFC v2 -> RFC v3:
> - Split into small patches (Jason);
> - Add helper virtqueue_use_indirect() (Jason);
> - Just set id for the last descriptor of a list (Jason);
> - Calculate the prev in virtqueue_add_packed() (Jason);
> - Fix/improve desc suppression code (Jason/MST);
> - Refine the code layout for XXX_split/packed and wrappers (MST);
> - Fix the comments and API in uapi (MST);
> - Remove the BUG_ON() for indirect (Jason);
> - Some other refinements and bug fixes;
>
> RFC v1 -> RFC v2:
> - Add indirect descriptor support - compile test only;
> - Add event suppression supprt - compile test only;
> - Move vring_packed_init() out of uapi (Jason, MST);
> - Merge two loops into one in virtqueue_add_packed() (Jason);
> - Split vring_unmap_one() for packed ring and split ring (Jason);
> - Avoid using '%' operator (Jason);
> - Rename free_head -> next_avail_idx (Jason);
> - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
> - Some other refinements and bug fixes;
>
> Thanks!
>
> Tiwei Bie (5):
>    virtio: add packed ring definitions
>    virtio_ring: support creating packed ring
>    virtio_ring: add packed ring support
>    virtio_ring: add event idx support in packed ring
>    virtio_ring: enable packed ring
>
>   drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
>   include/linux/virtio_ring.h        |    8 +-
>   include/uapi/linux/virtio_config.h |   12 +-
>   include/uapi/linux/virtio_ring.h   |   36 +
>   4 files changed, 1049 insertions(+), 278 deletions(-)
>

Re: [RFC v3 0/5] virtio: support packed ring

[Jason Wang]

On 2018年04月25日 13:15, Tiwei Bie wrote:
> Hello everyone,
>
> This RFC implements packed ring support in virtio driver.
>
> Some simple functional tests have been done with Jason's
> packed ring implementation in vhost:
>
> https://lkml.org/lkml/2018/4/23/12
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). But there are below known issues:
>
> 1. Reloading the guest driver will break the Tx/Rx;

Will have a look at this issue.

> 2. Zeroing the flags when detaching a used desc will
>     break the guest -> host path.

I still think zeroing flags is unnecessary or even a bug. At host, I 
track last observed avail wrap counter and detect avail like (what is 
suggested in the example code in the spec):

static bool desc_is_avail(struct vhost_virtqueue *vq, __virtio16 flags)
{
        bool avail = flags & cpu_to_vhost16(vq, DESC_AVAIL);

        return avail == vq->avail_wrap_counter;
}

So zeroing wrap can not work with this obviously.

Thanks

>
> Some simple functional tests have also been done with
> Wei's packed ring implementation in QEMU:
>
> http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html
>
> Both of ping and netperf worked as expected (with EVENT_IDX
> disabled). Reloading the guest driver also worked as expected.
>
> TODO:
> - Refinements (for code and commit log) and bug fixes;
> - Discuss/fix/test EVENT_IDX support;
> - Test devices other than net;
>
> RFC v2 -> RFC v3:
> - Split into small patches (Jason);
> - Add helper virtqueue_use_indirect() (Jason);
> - Just set id for the last descriptor of a list (Jason);
> - Calculate the prev in virtqueue_add_packed() (Jason);
> - Fix/improve desc suppression code (Jason/MST);
> - Refine the code layout for XXX_split/packed and wrappers (MST);
> - Fix the comments and API in uapi (MST);
> - Remove the BUG_ON() for indirect (Jason);
> - Some other refinements and bug fixes;
>
> RFC v1 -> RFC v2:
> - Add indirect descriptor support - compile test only;
> - Add event suppression supprt - compile test only;
> - Move vring_packed_init() out of uapi (Jason, MST);
> - Merge two loops into one in virtqueue_add_packed() (Jason);
> - Split vring_unmap_one() for packed ring and split ring (Jason);
> - Avoid using '%' operator (Jason);
> - Rename free_head -> next_avail_idx (Jason);
> - Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
> - Some other refinements and bug fixes;
>
> Thanks!
>
> Tiwei Bie (5):
>    virtio: add packed ring definitions
>    virtio_ring: support creating packed ring
>    virtio_ring: add packed ring support
>    virtio_ring: add event idx support in packed ring
>    virtio_ring: enable packed ring
>
>   drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
>   include/linux/virtio_ring.h        |    8 +-
>   include/uapi/linux/virtio_config.h |   12 +-
>   include/uapi/linux/virtio_ring.h   |   36 +
>   4 files changed, 1049 insertions(+), 278 deletions(-)
>

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[RFC v3 0/5] virtio: support packed ring

[Tiwei Bie]

Hello everyone,

This RFC implements packed ring support in virtio driver.

Some simple functional tests have been done with Jason's
packed ring implementation in vhost:

https://lkml.org/lkml/2018/4/23/12

Both of ping and netperf worked as expected (with EVENT_IDX
disabled). But there are below known issues:

1. Reloading the guest driver will break the Tx/Rx;
2. Zeroing the flags when detaching a used desc will
   break the guest -> host path.

Some simple functional tests have also been done with
Wei's packed ring implementation in QEMU:

http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg00342.html

Both of ping and netperf worked as expected (with EVENT_IDX
disabled). Reloading the guest driver also worked as expected.

TODO:
- Refinements (for code and commit log) and bug fixes;
- Discuss/fix/test EVENT_IDX support;
- Test devices other than net;

RFC v2 -> RFC v3:
- Split into small patches (Jason);
- Add helper virtqueue_use_indirect() (Jason);
- Just set id for the last descriptor of a list (Jason);
- Calculate the prev in virtqueue_add_packed() (Jason);
- Fix/improve desc suppression code (Jason/MST);
- Refine the code layout for XXX_split/packed and wrappers (MST);
- Fix the comments and API in uapi (MST);
- Remove the BUG_ON() for indirect (Jason);
- Some other refinements and bug fixes;

RFC v1 -> RFC v2:
- Add indirect descriptor support - compile test only;
- Add event suppression supprt - compile test only;
- Move vring_packed_init() out of uapi (Jason, MST);
- Merge two loops into one in virtqueue_add_packed() (Jason);
- Split vring_unmap_one() for packed ring and split ring (Jason);
- Avoid using '%' operator (Jason);
- Rename free_head -> next_avail_idx (Jason);
- Add comments for virtio_wmb() in virtqueue_add_packed() (Jason);
- Some other refinements and bug fixes;

Thanks!

Tiwei Bie (5):
  virtio: add packed ring definitions
  virtio_ring: support creating packed ring
  virtio_ring: add packed ring support
  virtio_ring: add event idx support in packed ring
  virtio_ring: enable packed ring

 drivers/virtio/virtio_ring.c       | 1271 ++++++++++++++++++++++++++++--------
 include/linux/virtio_ring.h        |    8 +-
 include/uapi/linux/virtio_config.h |   12 +-
 include/uapi/linux/virtio_ring.h   |   36 +
 4 files changed, 1049 insertions(+), 278 deletions(-)

-- 
2.11.0