linux-kernel - Re: [PATCH RFC 2/2] vhost: packed ring support

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Date:   Wed, 28 Feb 2018 10:38:36 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Tiwei Bie <tiwei.bie@...el.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        wexu@...hat.com, jfreimann@...hat.com
Subject: Re: [PATCH RFC 2/2] vhost: packed ring support



On 2018年02月27日 17:03, Tiwei Bie wrote:
> On Wed, Feb 14, 2018 at 10:37:09AM +0800, Jason Wang wrote:
> [...]
>> +static void set_desc_used(struct vhost_virtqueue *vq,
>> +			  struct vring_desc_packed *desc, bool wrap_counter)
>> +{
>> +	__virtio16 flags = desc->flags;
>> +
>> +	if (wrap_counter) {
>> +		desc->flags |= cpu_to_vhost16(vq, DESC_AVAIL);
>> +		desc->flags |= cpu_to_vhost16(vq, DESC_USED);
>> +	} else {
>> +		desc->flags &= ~cpu_to_vhost16(vq, DESC_AVAIL);
>> +		desc->flags &= ~cpu_to_vhost16(vq, DESC_USED);
>> +	}
>> +
>> +	desc->flags = flags;
> The `desc->flags` is restored after the change.

Right, will fix.

>> +}
>> +
>> +static int vhost_get_vq_desc_packed(struct vhost_virtqueue *vq,
>> +				    struct iovec iov[], unsigned int iov_size,
>> +				    unsigned int *out_num, unsigned int *in_num,
>> +				    struct vhost_log *log,
>> +				    unsigned int *log_num)
>> +{
>> +	struct vring_desc_packed desc;
>> +	int ret, access, i;
>> +	u16 avail_idx = vq->last_avail_idx;
>> +
>> +	/* When we start there are none of either input nor output. */
>> +	*out_num = *in_num = 0;
>> +	if (unlikely(log))
>> +		*log_num = 0;
>> +
>> +	do {
>> +		unsigned int iov_count = *in_num + *out_num;
>> +
>> +		i = vq->last_avail_idx & (vq->num - 1);
> The queue size may not be a power of 2 in packed ring.

Will fix this too.

Thanks

> Best regards,
> Tiwei Bie