[dpdk-dev] [PATCH 3/4] vhost: log vring changes

Victor Kaplansky victork at redhat.com
Wed Dec 2 16:58:24 CET 2015


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.

> 
> 	--yliu


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