From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH 3/4] vhost: log vring changes
Date: Wed, 2 Dec 2015 18:26:37 +0200
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To: Victor Kaplansky <victork@redhat.com>
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On Wed, Dec 02, 2015 at 05:58:24PM +0200, Victor Kaplansky wrote:
> On Wed, Dec 02, 2015 at 10:38:02PM +0800, Yuanhan Liu wrote:
> > On Wed, Dec 02, 2015 at 04:07:02PM +0200, Victor Kaplansky wrote:
> > > On Wed, Dec 02, 2015 at 11:43:12AM +0800, Yuanhan Liu wrote:
> > > > Invoking vhost_log_write() to mark corresponding page as dirty while
> > > > updating used vring.
> > > 
> > > Looks good, thanks!
> > > 
> > > I didn't find where you log the dirty pages in result of data
> > > written to the buffers pointed by the descriptors in RX vring.
> > > AFAIU, the buffers of RX queue reside in guest's memory and have
> > > to be marked as dirty if they are written. What do you say?
> > 
> > Yeah, we should. I got a question then: why log_guest_addr is set
> > to the physical address of used vring in guest? I mean, apparently,
> > we need log more changes other than used vring only.
> 
> The physical address of used vring sent to the back-end, since
> otherwise back-end has to perform virtual to physical
> translation, and we want to avoid this. The dirty buffers has to
> be marked as well, but their guest's physical address is known
> directly from the descriptors.

Yes, people wanted to be able to do multiple physical
addresses to one virtual so you do not want to translate
virt to phys.

> > 
> > 	--yliu