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From: Stefan Hajnoczi <stefanha@redhat.com>
To: michael.christie@oracle.com
Cc: Jason Wang <jasowang@redhat.com>,
	target-devel@vger.kernel.org, linux-scsi@vger.kernel.org,
	pbonzini@redhat.com, mst@redhat.com, sgarzare@redhat.com,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH V3 11/11] vhost: allow userspace to create workers
Date: Wed, 27 Oct 2021 10:03:43 +0100	[thread overview]
Message-ID: <YXkV73jK7fNGzcoX@stefanha-x1.localdomain> (raw)
In-Reply-To: <4d33b7e1-5efb-3729-ee15-98608704f096@oracle.com>

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On Tue, Oct 26, 2021 at 11:49:37AM -0500, michael.christie@oracle.com wrote:
> On 10/26/21 12:37 AM, Jason Wang wrote:
> > Do we need VHOST_VRING_FREE_WORKER? And I wonder if using dedicated ioctls are better:
> > 
> > VHOST_VRING_NEW/FREE_WORKER
> > VHOST_VRING_ATTACH_WORKER
> 
> 
> We didn't need a free worker, because the kernel handles it for userspace. I
> tried to make it easy for userspace because in some cases it may not be able
> to do syscalls like close on the device. For example if qemu crashes or for
> vhost-scsi we don't do an explicit close during VM shutdown.
> 
> So we start off with the default worker thread that's used by all vqs like we do
> today. Userspace can then override it by creating a new worker. That also unbinds/
> detaches the existing worker and does a put on the workers refcount. We also do a
> put on the worker when we stop using it during device shutdown/closure/release.
> When the worker's refcount goes to zero the kernel deletes it.

Please document the worker (p)id lifetime for the ioctl. Otherwise
userspace doesn't know whether a previously created worker is still
alive.

SSTefan

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WARNING: multiple messages have this Message-ID (diff)
From: Stefan Hajnoczi <stefanha@redhat.com>
To: michael.christie@oracle.com
Cc: linux-scsi@vger.kernel.org, mst@redhat.com,
	virtualization@lists.linux-foundation.org,
	target-devel@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH V3 11/11] vhost: allow userspace to create workers
Date: Wed, 27 Oct 2021 10:03:43 +0100	[thread overview]
Message-ID: <YXkV73jK7fNGzcoX@stefanha-x1.localdomain> (raw)
In-Reply-To: <4d33b7e1-5efb-3729-ee15-98608704f096@oracle.com>


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On Tue, Oct 26, 2021 at 11:49:37AM -0500, michael.christie@oracle.com wrote:
> On 10/26/21 12:37 AM, Jason Wang wrote:
> > Do we need VHOST_VRING_FREE_WORKER? And I wonder if using dedicated ioctls are better:
> > 
> > VHOST_VRING_NEW/FREE_WORKER
> > VHOST_VRING_ATTACH_WORKER
> 
> 
> We didn't need a free worker, because the kernel handles it for userspace. I
> tried to make it easy for userspace because in some cases it may not be able
> to do syscalls like close on the device. For example if qemu crashes or for
> vhost-scsi we don't do an explicit close during VM shutdown.
> 
> So we start off with the default worker thread that's used by all vqs like we do
> today. Userspace can then override it by creating a new worker. That also unbinds/
> detaches the existing worker and does a put on the workers refcount. We also do a
> put on the worker when we stop using it during device shutdown/closure/release.
> When the worker's refcount goes to zero the kernel deletes it.

Please document the worker (p)id lifetime for the ioctl. Otherwise
userspace doesn't know whether a previously created worker is still
alive.

SSTefan

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  parent reply	other threads:[~2021-10-27  9:03 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-22  5:18 [PATCH V3 00/11] vhost: multiple worker support Mike Christie
2021-10-22  5:18 ` Mike Christie
2021-10-22  5:19 ` [PATCH] QEMU vhost-scsi: add support for VHOST_SET_VRING_WORKER Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 01/11] vhost: add vhost_worker pointer to vhost_virtqueue Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 02/11] vhost, vhost-net: add helper to check if vq has work Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 03/11] vhost: take worker or vq instead of dev for queueing Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 04/11] vhost: take worker or vq instead of dev for flushing Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 05/11] vhost: convert poll work to be vq based Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 06/11] vhost-sock: convert to vq helpers Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-25  9:08   ` Stefano Garzarella
2021-10-25  9:08     ` Stefano Garzarella
2021-10-25 16:09     ` michael.christie
2021-10-25 16:09       ` michael.christie
2021-10-22  5:19 ` [PATCH V3 07/11] vhost-scsi: make SCSI cmd completion per vq Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 08/11] vhost-scsi: convert to vq helpers Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 09/11] vhost-scsi: flush IO vqs then send TMF rsp Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 10/11] vhost: remove device wide queu/flushing helpers Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22  5:19 ` [PATCH V3 11/11] vhost: allow userspace to create workers Mike Christie
2021-10-22  5:19   ` Mike Christie
2021-10-22 10:47   ` Michael S. Tsirkin
2021-10-22 10:47     ` Michael S. Tsirkin
2021-10-22 16:12     ` michael.christie
2021-10-22 16:12       ` michael.christie
2021-10-22 18:17       ` michael.christie
2021-10-22 18:17         ` michael.christie
2021-10-23 20:11         ` Michael S. Tsirkin
2021-10-23 20:11           ` Michael S. Tsirkin
2021-10-25 16:04           ` michael.christie
2021-10-25 16:04             ` michael.christie
2021-10-25 17:14             ` Michael S. Tsirkin
2021-10-25 17:14               ` Michael S. Tsirkin
2021-10-26  5:37   ` Jason Wang
2021-10-26  5:37     ` Jason Wang
2021-10-26 13:09     ` Michael S. Tsirkin
2021-10-26 13:09       ` Michael S. Tsirkin
2021-10-26 16:36       ` Stefan Hajnoczi
2021-10-26 16:36         ` Stefan Hajnoczi
2021-10-26 15:44     ` Stefan Hajnoczi
2021-10-26 15:44       ` Stefan Hajnoczi
2021-10-27  2:55       ` Jason Wang
2021-10-27  2:55         ` Jason Wang
2021-10-27  9:01         ` Stefan Hajnoczi
2021-10-27  9:01           ` Stefan Hajnoczi
2021-10-26 16:49     ` michael.christie
2021-10-26 16:49       ` michael.christie
2021-10-27  6:02       ` Jason Wang
2021-10-27  6:02         ` Jason Wang
2021-10-27  9:03       ` Stefan Hajnoczi [this message]
2021-10-27  9:03         ` Stefan Hajnoczi
2021-10-26 15:22   ` Stefan Hajnoczi
2021-10-26 15:22     ` Stefan Hajnoczi
2021-10-26 15:24   ` Stefan Hajnoczi
2021-10-26 15:24     ` Stefan Hajnoczi
2021-10-22  6:02 ` [PATCH V3 00/11] vhost: multiple worker support michael.christie
2021-10-22  6:02   ` michael.christie
2021-10-22  9:49   ` Michael S. Tsirkin
2021-10-22  9:49     ` Michael S. Tsirkin
2021-10-22  9:48 ` Michael S. Tsirkin
2021-10-22  9:48   ` Michael S. Tsirkin
2021-10-22 15:54   ` michael.christie
2021-10-22 15:54     ` michael.christie
2021-10-23 20:12     ` Michael S. Tsirkin
2021-10-23 20:12       ` Michael S. Tsirkin

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