From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Date: Thu, 24 Sep 2020 07:22:47 +0000 Subject: Re: [PATCH 2/8] vhost: add helper to check if a vq has been setup Message-Id: List-Id: References: <1600712588-9514-1-git-send-email-michael.christie@oracle.com> <1600712588-9514-3-git-send-email-michael.christie@oracle.com> <63094bae-1f26-c21e-9b3c-3a6aa99a7e24@oracle.com> In-Reply-To: <63094bae-1f26-c21e-9b3c-3a6aa99a7e24@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Mike Christie , 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 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 >>> --- >>>   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 >