Re: [Qemu-devel] [PATCH RFC v4 16/20] intel_iommu: do replay when context invalidate

[Peter Xu <peterx@redhat.com>]

On Wed, Jan 25, 2017 at 06:37:23AM +0000, Tian, Kevin wrote:
> > From: Peter Xu [mailto:peterx@redhat.com]
> > Sent: Wednesday, January 25, 2017 11:46 AM
> > 
> > On Wed, Jan 25, 2017 at 11:09:39AM +0800, Jason Wang wrote:
> > >
> > >
> > > On 2017年01月24日 12:52, Peter Xu wrote:
> > > >On Mon, Jan 23, 2017 at 06:36:17PM +0800, Jason Wang wrote:
> > > >>
> > > >>On 2017年01月20日 21:08, Peter Xu wrote:
> > > >>>Before this one we only invalidate context cache when we receive context
> > > >>>entry invalidations. However it's possible that the invalidation also
> > > >>>contains a domain switch (only if cache-mode is enabled for vIOMMU). In
> > > >>>that case we need to notify all the registered components about the new
> > > >>>mapping.
> > > >>>
> > > >>>Signed-off-by: Peter Xu <peterx@redhat.com>
> > > >>>---
> > > >>>  hw/i386/intel_iommu.c | 10 ++++++++++
> > > >>>  1 file changed, 10 insertions(+)
> > > >>>
> > > >>>diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > > >>>index f9c5142..4b08b4d 100644
> > > >>>--- a/hw/i386/intel_iommu.c
> > > >>>+++ b/hw/i386/intel_iommu.c
> > > >>>@@ -1146,6 +1146,16 @@ static void
> > vtd_context_device_invalidate(IntelIOMMUState *s,
> > > >>>                  trace_vtd_inv_desc_cc_device(bus_n, VTD_PCI_SLOT(devfn_it),
> > > >>>                                               VTD_PCI_FUNC(devfn_it));
> > > >>>                  vtd_as->context_cache_entry.context_cache_gen = 0;
> > > >>>+                /*
> > > >>>+                 * So a device is moving out of (or moving into) a
> > > >>>+                 * domain, a replay() suites here to notify all the
> > > >>>+                 * IOMMU_NOTIFIER_MAP registers about this change.
> > > >>>+                 * This won't bring bad even if we have no such
> > > >>>+                 * notifier registered - the IOMMU notification
> > > >>>+                 * framework will skip MAP notifications if that
> > > >>>+                 * happened.
> > > >>>+                 */
> > > >>>+                memory_region_iommu_replay_all(&vtd_as->iommu);
> > > >>DSI and GLOBAL questions come back again or no need to care about them :) ?
> > > >DSI/GLOBAL hanldings are in patch 20 (though it'll be squashed into 18
> > > >in my next post). Is that what you mean above?
> > >
> > > Seems not, I mean DSI/GLOBAL for context cache invalidation instead of IOTLB
> > > :)
> > 
> > Yes, I should possibly do the same thing for context cache global
> > invalidations. IIUC context global invalidation should be a superset
> > of iotlb invalidation, so maybe I'll add one more patch to call iotlb
> > invalidation in context invalidation as well. Kevin/others, please
> > correct me if I misunderstood the spec. Thanks,
> > 
> 
> context invalidation is not superset of iotlb invalidation. The spec just
> requires software to always follow a context-cache invalidation with
> a PASID-cache invalidation, followed by an IOTLB invalidation.

Thanks for pointing out. If so, looks like current version suffice for
this, right? (so no further change needed for this one)

-- peterx