[RFC PATCH] vhost: enable IOMMU_NOTIFIER_UNMAP events handling when device-iotlb=on

[Viktor Prutyanov]

Even if Device-TLB and PCI ATS is enabled, the guest can reject to use
it. For example, this situation appears when Windows Server 2022 is
running with intel-iommu with device-iotlb=on and virtio-net-pci with
vhost=on. The guest implies that no address translation info cached in
device IOTLB and doesn't send device IOTLB invalidation commands. So,
it leads to irrelevant address translations in vhost-net in the host
kernel. Therefore network frames from the guest in host tap interface
contains wrong payload data.

This patch enables IOTLB unmap events (IOMMU_NOTIFIER_UNMAP) along with
Device-TLB unmap events (IOMMU_NOTIFIER_DEVIOTLB_UNMAP) handling for
proper vhost IOTLB unmapping when the guest isn't aware of Device-TLB.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2001312
Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
---

 Tested on Windows Server 2022 and Fedora guests with
 -device virtio-net-pci,bus=pci.3,netdev=nd0,iommu_platform=on,ats=on
 -netdev tap,id=nd0,ifname=tap1,script=no,downscript=no,vhost=on
 -device intel-iommu,intremap=on,eim=on,device-iotlb=on/off

 hw/virtio/vhost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index a266396576..968ca18fce 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -796,7 +796,7 @@ static void vhost_iommu_region_add(MemoryListener *listener,
     iommu_idx = memory_region_iommu_attrs_to_index(iommu_mr,
                                                    MEMTXATTRS_UNSPECIFIED);
     iommu_notifier_init(&iommu->n, vhost_iommu_unmap_notify,
-                        IOMMU_NOTIFIER_DEVIOTLB_UNMAP,
+                        IOMMU_NOTIFIER_DEVIOTLB_UNMAP | IOMMU_NOTIFIER_UNMAP,
                         section->offset_within_region,
                         int128_get64(end),
                         iommu_idx);
-- 
2.35.1