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

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Wed, Dec 02, 2015 at 06:26:37PM +0200, Michael S. Tsirkin wrote:
> 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.

Thank you both, it's clear to me then.

	--yliu