Re: [Qemu-devel] [PATCH v3 12/12] intel-iommu: new sync_shadow_page_table

[Peter Xu]

On Fri, May 18, 2018 at 12:06:14AM +0300, Michael S. Tsirkin wrote:
> On Thu, May 17, 2018 at 04:59:27PM +0800, Peter Xu wrote:
> > Firstly, introduce the sync_shadow_page_table() helper to resync the
> > whole shadow page table of an IOMMU address space.  Meanwhile, when we
> > receive domain invalidation or similar requests (for example, context
> > entry invalidations, global invalidations, ...), we should not really
> > run the replay logic, instead we can now use the new sync shadow page
> > table API to resync the whole shadow page table.
> > 
> > There will be two major differences:
> > 
> > 1. We don't unmap-all before walking the page table, we just sync.  The
> >    global unmap-all can create a very small window that the page table
> >    is invalid or incomplete
> 
> The implication is that with vfio, device might stop working
> without this change.

I guess it was working before.  However patch 9 changed the page
walking to be state-ful since we have IOVA tree now (it was not) so we
might encounter the scp DMA error after patch 9.  I still kept the
patches 9-12 to be separate since logically they are isolated.
However if you want maybe we can also squash 9-12 patches into one
single (but a bit huge) patch.

Thanks,

-- 
Peter Xu