From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Tokarev <mjt@tls.msk.ru>
Subject: Re: [PATCH] virtio-blk: fallback to draining the queue if barrier
 ops are not supported
Date: Wed, 14 Oct 2009 19:38:45 +0400
Message-ID: <4AD5F085.8040909@msgid.tls.msk.ru>
References: <4AD5B00D.102@redhat.com> <1255521788-24346-1-git-send-email-avi@redhat.com>
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Cc: Christoph Hellwig <hch@lst.de>,
	Matthew Tippett <tippettm@gmail.com>,
	Dustin Kirkland <dustin.kirkland@gmail.com>,
	Anthony Liguori <anthony@codemonkey.ws>, RW <kvm@tauceti.net>,
	kvm@vger.kernel.org
To: Avi Kivity <avi@redhat.com>
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Avi Kivity wrote:
> Early implementations of virtio devices did not support barrier operations,
> but did commit the data to disk.  In such cases, drain the queue to emulate
> barrier operations.

Are there any implementation currently that actually supports barriers?
As far as I remember there's no way to invoke barriers from a user-space
application on linux, and this is how kvm/qemu is running on this OS.

Thanks!

/mjt