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From: Hannes Reinecke <hare@suse.de>
To: Dongli Zhang <dongli.zhang@oracle.com>,
	virtualization@lists.linux-foundation.org,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-block@vger.kernel.org
Cc: mst@redhat.com, jasowang@redhat.com, pbonzini@redhat.com,
	stefanha@redhat.com, jejb@linux.ibm.com,
	martin.petersen@oracle.com, joe.jin@oracle.com,
	junxiao.bi@oracle.com, srinivas.eeda@oracle.com
Subject: Re: [RFC] virtio_scsi: to poll and kick the virtqueue in timeout handler
Date: Sun, 23 May 2021 09:39:51 +0200	[thread overview]
Message-ID: <ac161748-15d2-2962-402e-23abca469623@suse.de> (raw)
In-Reply-To: <20210523063843.1177-1-dongli.zhang@oracle.com>

On 5/23/21 8:38 AM, Dongli Zhang wrote:
> This RFC is to trigger the discussion about to poll and kick the
> virtqueue on purpose in virtio-scsi timeout handler.
> 
> The virtio-scsi relies on the virtio vring shared between VM and host.
> The VM side produces requests to vring and kicks the virtqueue, while the
> host side produces responses to vring and interrupts the VM side.
> 
> By default the virtio-scsi handler depends on the host timeout handler
> by BLK_EH_RESET_TIMER to give host a chance to perform EH.
> 
> However, this is not helpful for the case that the responses are available
> on vring but the notification from host to VM is lost.
> 
How can this happen?
If responses are lost the communication between VM and host is broken, 
and we should rather reset the virtio rings themselves.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

WARNING: multiple messages have this Message-ID (diff)
From: Hannes Reinecke <hare@suse.de>
To: Dongli Zhang <dongli.zhang@oracle.com>,
	virtualization@lists.linux-foundation.org,
	linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-block@vger.kernel.org
Cc: martin.petersen@oracle.com, mst@redhat.com, joe.jin@oracle.com,
	junxiao.bi@oracle.com, stefanha@redhat.com, pbonzini@redhat.com,
	srinivas.eeda@oracle.com, jejb@linux.ibm.com
Subject: Re: [RFC] virtio_scsi: to poll and kick the virtqueue in timeout handler
Date: Sun, 23 May 2021 09:39:51 +0200	[thread overview]
Message-ID: <ac161748-15d2-2962-402e-23abca469623@suse.de> (raw)
In-Reply-To: <20210523063843.1177-1-dongli.zhang@oracle.com>

On 5/23/21 8:38 AM, Dongli Zhang wrote:
> This RFC is to trigger the discussion about to poll and kick the
> virtqueue on purpose in virtio-scsi timeout handler.
> 
> The virtio-scsi relies on the virtio vring shared between VM and host.
> The VM side produces requests to vring and kicks the virtqueue, while the
> host side produces responses to vring and interrupts the VM side.
> 
> By default the virtio-scsi handler depends on the host timeout handler
> by BLK_EH_RESET_TIMER to give host a chance to perform EH.
> 
> However, this is not helpful for the case that the responses are available
> on vring but the notification from host to VM is lost.
> 
How can this happen?
If responses are lost the communication between VM and host is broken, 
and we should rather reset the virtio rings themselves.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
_______________________________________________
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Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  reply	other threads:[~2021-05-23  7:39 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-23  6:38 [RFC] virtio_scsi: to poll and kick the virtqueue in timeout handler Dongli Zhang
2021-05-23  6:38 ` Dongli Zhang
2021-05-23  7:39 ` Hannes Reinecke [this message]
2021-05-23  7:39   ` Hannes Reinecke
2021-05-24 13:24   ` Stefan Hajnoczi
2021-05-24 13:24     ` Stefan Hajnoczi
2021-05-25  6:33     ` Dongli Zhang
2021-05-25  6:33       ` Dongli Zhang
2021-05-25 16:47       ` Stefan Hajnoczi
2021-05-25 16:47         ` Stefan Hajnoczi
2021-05-25 17:24         ` Hannes Reinecke
2021-05-25 17:24           ` Hannes Reinecke
2021-05-25 17:34           ` Dongli Zhang
2021-05-25 17:34             ` Dongli Zhang

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