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SubjectRe: [RFC V4 PATCH 7/8] vhost: packed ring support
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On 2018年05月23日 15:17, Wei Xu wrote:
> On Wed, May 23, 2018 at 09:39:28AM +0800, Jason Wang wrote:
>>
>> On 2018年05月23日 00:54, Wei Xu wrote:
>>> On Wed, May 16, 2018 at 08:32:20PM +0800, Jason Wang wrote:
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>> ---
>>>> drivers/vhost/net.c | 3 +-
>>>> drivers/vhost/vhost.c | 539 ++++++++++++++++++++++++++++++++++++++++++++++----
>>>> drivers/vhost/vhost.h | 8 +-
>>>> 3 files changed, 513 insertions(+), 37 deletions(-)
>>>>
>>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>>>> index 8304c30..f2a0f5b 100644
>>>> --- a/drivers/vhost/vhost.c
>>>> +++ b/drivers/vhost/vhost.c
>>>> @@ -1358,6 +1382,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
>>>> break;
>>>> }
>>>> vq->last_avail_idx = s.num;
>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
>>>> + vq->avail_wrap_counter = s.num >> 31;
>>>> /* Forget the cached index value. */
>>>> vq->avail_idx = vq->last_avail_idx;
>>>> break;
>>>> @@ -1366,6 +1392,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
>>>> s.num = vq->last_avail_idx;
>>>> if (copy_to_user(argp, &s, sizeof s))
>>>> r = -EFAULT;
>>>> + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
>>>> + s.num |= vq->avail_wrap_counter << 31;
>>>> break;
>>>> case VHOST_SET_VRING_ADDR:
>>>> if (copy_from_user(&a, argp, sizeof a)) {
>>> 'last_used_idx' also needs to be saved/restored here.
>>>
>>> I have figured out the root cause of broken device after reloading
>>> 'virtio-net' module, all indices have been reset for a reloading but
>>> 'last_used_idx' is not properly reset in this case. This confuses
>>> handle_rx()/tx().
>>>
>>> Wei
>>>
>> Good catch, so we probably need a new ioctl to sync between qemu and vhost.
>>
>> Something like VHOST_SET/GET_USED_BASE.
> Sure, or can we expand 'vhost_vring_state' to keep them done in a bunch?

It's port of uapi, so we can't.

Thanks

>
>> Thanks
>>

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