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From: Jason Wang <jasowang@redhat.com>
To: Mike Christie <michael.christie@oracle.com>,
	martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
	target-devel@vger.kernel.org, mst@redhat.com,
	pbonzini@redhat.com, stefanha@redhat.com,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 2/8] vhost: add helper to check if a vq has been setup
Date: Thu, 24 Sep 2020 15:22:47 +0800
Message-ID: <e81db364-8b9e-bd01-5d22-3fd52375c8d3@redhat.com> (raw)
In-Reply-To: <63094bae-1f26-c21e-9b3c-3a6aa99a7e24@oracle.com>


On 2020/9/24 上午3:12, Mike Christie wrote:
> On 9/21/20 9:02 PM, Jason Wang wrote:
>> On 2020/9/22 上午2:23, Mike Christie wrote:
>>> This adds a helper check if a vq has been setup. The next patches
>>> will use this when we move the vhost scsi cmd preallocation from per
>>> session to per vq. In the per vq case, we only want to allocate cmds
>>> for vqs that have actually been setup and not for all the possible
>>> vqs.
>>>
>>> Signed-off-by: Mike Christie <michael.christie@oracle.com>
>>> ---
>>>    drivers/vhost/vhost.c | 9 +++++++++
>>>    drivers/vhost/vhost.h | 1 +
>>>    2 files changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>>> index b45519c..5dd9eb1 100644
>>> --- a/drivers/vhost/vhost.c
>>> +++ b/drivers/vhost/vhost.c
>>> @@ -305,6 +305,15 @@ static void vhost_vring_call_reset(struct vhost_vring_call *call_ctx)
>>>        spin_lock_init(&call_ctx->ctx_lock);
>>>    }
>>>    +bool vhost_vq_is_setup(struct vhost_virtqueue *vq)
>>> +{
>>> +    if (vq->avail && vq->desc && vq->used && vhost_vq_access_ok(vq))
>>> +        return true;
>>> +    else
>>> +        return false;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vhost_vq_is_setup);
>>
>> This is probably ok but I wonder maybe we should have something like what vDPA did (VHOST_SET_VRING_ENABLE) to match virtio 1.0 device definition.
> It looks like I can make that work. Some questions:
>
> 1. Do you mean a generic VHOST_SET_VRING_ENABLE or a SCSI specific one VHOST_SCSI_SET_VRING_ENABLE?


It would be better if we can make it generic.


>
> 2. I can see the VHOST_VDPA_SET_VRING_ENABLE kernel code and the vhost_set_vring_enable qemu code, so I have an idea of how it should work for vhost scsi. However, I'm not sure the requirements for a generic VHOST_SET_VRING_ENABLE if that is what you meant. I could not find it in the spec either. Could you send me a pointer to the section?


In the spec, for PCI, it's the queue_enable for modern device.


>
> For example, for vhost-net we seem to enable a device in the VHOST_NET_SET_BACKEND ioctl, so I'm not sure what behavior should be or needs to be implemented for net and vsock.


Yes, but VHOST_NET_SET_BACKEND is for the whole device not a specific 
virtqueue.


Thanks


>


  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-21 18:23 [PATCH 0/8] vhost scsi: fixes and cleanups Mike Christie
2020-09-21 18:23 ` [PATCH 1/8] vhost vdpa: fix vhost_vdpa_open error handling Mike Christie
2020-09-22  1:58   ` Jason Wang
2020-09-21 18:23 ` [PATCH 2/8] vhost: add helper to check if a vq has been setup Mike Christie
2020-09-22  2:02   ` Jason Wang
2020-09-23 19:12     ` Mike Christie
2020-09-24  7:22       ` Jason Wang [this message]
2020-09-22  2:45   ` Bart Van Assche
2020-09-22 15:34     ` Michael Christie
2020-09-21 18:23 ` [PATCH 3/8] vhost scsi: alloc cmds per vq instead of session Mike Christie
2020-09-22  1:32   ` kernel test robot
2020-09-23  7:53   ` Dan Carpenter
2020-09-24  6:22   ` Michael S. Tsirkin
2020-09-24 15:31     ` Michael Christie
2020-09-21 18:23 ` [PATCH 4/8] vhost scsi: fix cmd completion race Mike Christie
2020-09-22  2:48   ` Bart Van Assche
2020-09-22  2:51     ` Bart Van Assche
2020-09-21 18:23 ` [PATCH 5/8] vhost scsi: add lun parser helper Mike Christie
2020-09-23 10:23   ` Paolo Bonzini
2020-09-21 18:23 ` [PATCH 6/8] vhost scsi: Add support for LUN resets Mike Christie
2020-09-21 18:23 ` [PATCH 7/8] vhost: remove work arg from vhost_work_flush Mike Christie
2020-09-22  2:01   ` Jason Wang
2020-09-21 18:23 ` [PATCH 8/8] vhost scsi: remove extra flushes Mike Christie

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