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

From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH RFC v4 16/20] intel_iommu: do replay when context invalidate
Date: Wed, 25 Jan 2017 15:45:01 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1

On 2017年01月25日 14:44, Peter Xu wrote:
On Wed, Jan 25, 2017 at 06:37:23AM +0000, Tian, Kevin wrote:
From: Peter Xu [mailto:address@hidden
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

Signed-off-by: Peter Xu <address@hidden>
  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_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

We could not depends on guest or driver behavior. I still prefer to add unamp for DSI/GLOBAL to prevent us from leaking mappings.


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