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From f7e1caa3302f705abe196b8a021cfa52750749ff Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Thu, 8 Nov 2018 06:29:38 +0000
Subject: [PATCH 10/35] intel_iommu: handle invalid ce for shadow sync

RH-Author: Peter Xu <peterx@redhat.com>
Message-id: <20181108062938.21143-8-peterx@redhat.com>
Patchwork-id: 82966
O-Subject: [RHEL-8 qemu-kvm PATCH 7/7] intel_iommu: handle invalid ce for shadow sync
Bugzilla: 1625173
RH-Acked-by: Auger Eric <eric.auger@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

Bugzilla: 1629616

We should handle VTD_FR_CONTEXT_ENTRY_P properly when synchronizing
shadow page tables.  Having invalid context entry there is perfectly
valid when we move a device out of an existing domain.  When that
happens, instead of posting an error we invalidate the whole region.

Without this patch, QEMU will crash if we do these steps:

(1) start QEMU with VT-d IOMMU and two 10G NICs (ixgbe)
(2) bind the NICs with vfio-pci in the guest
(3) start testpmd with the NICs applied
(4) stop testpmd
(5) rebind the NIC back to ixgbe kernel driver

The patch should fix it.

Reported-by: Pei Zhang <pezhang@redhat.com>
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1627272
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit c28b535d083d0a263d38d9ceeada83cdae8c64f0)
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 hw/i386/intel_iommu.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index c95128d..12af410 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -38,6 +38,7 @@
 #include "trace.h"
 
 static void vtd_address_space_refresh_all(IntelIOMMUState *s);
+static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n);
 
 static void vtd_define_quad(IntelIOMMUState *s, hwaddr addr, uint64_t val,
                             uint64_t wmask, uint64_t w1cmask)
@@ -1066,11 +1067,27 @@ static int vtd_sync_shadow_page_table(VTDAddressSpace *vtd_as)
 {
     int ret;
     VTDContextEntry ce;
+    IOMMUNotifier *n;
 
     ret = vtd_dev_to_context_entry(vtd_as->iommu_state,
                                    pci_bus_num(vtd_as->bus),
                                    vtd_as->devfn, &ce);
     if (ret) {
+        if (ret == -VTD_FR_CONTEXT_ENTRY_P) {
+            /*
+             * It's a valid scenario to have a context entry that is
+             * not present.  For example, when a device is removed
+             * from an existing domain then the context entry will be
+             * zeroed by the guest before it was put into another
+             * domain.  When this happens, instead of synchronizing
+             * the shadow pages we should invalidate all existing
+             * mappings and notify the backends.
+             */
+            IOMMU_NOTIFIER_FOREACH(n, &vtd_as->iommu) {
+                vtd_address_space_unmap(vtd_as, n);
+            }
+            ret = 0;
+        }
         return ret;
     }
 
-- 
1.8.3.1