An initial idea is that we can let IOMMU to export this information to vhost so
that vhost would know whether the vIOMMU would support dev-iotlb, then vhost
can conditionally register to dev-iotlb or the old iotlb way. We can work
based on some previous patch to introduce PCIIOMMUOps as Yi Liu proposed [1].
However it's not as easy as I thought since vhost_iommu_region_add() does not
have a PCIDevice context at all since it's completely a backend. It seems
non-trivial to pass over a PCI device to the backend during init. E.g. when
the IOMMU notifier registered hdev->vdev is still NULL.
To make the fix smaller and easier, this patch goes the other way to leverage
the flag_changed() hook of vIOMMUs so that SMMU and virtio-iommu can trap the
dev-iotlb registration and fail it. Then vhost could try the fallback solution
as using UNMAP invalidation for it's translations.
[1]
https://lore.kernel.org/qemu-devel/1599735398-6829-4-git-send-email-yi.l.liu@intel.com/
Reported-by: Eric Auger <eric.auger@redhat.com>
Fixes: b68ba1ca57677acf870d5ab10579e6105c1f5338
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
hw/arm/smmuv3.c | 5 +++++
hw/virtio/vhost.c | 13 +++++++++++--
hw/virtio/virtio-iommu.c | 5 +++++
3 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
index 98b99d4fe8e..bd1f97000d9 100644
--- a/hw/arm/smmuv3.c
+++ b/hw/arm/smmuv3.c
@@ -1497,6 +1497,11 @@ static int smmuv3_notify_flag_changed(IOMMUMemoryRegion
*iommu,
SMMUv3State *s3 = sdev->smmu;
SMMUState *s = &(s3->smmu_state);
+ if (new & IOMMU_NOTIFIER_DEVIOTLB_UNMAP) {
+ error_setg(errp, "SMMUv3 does not support dev-iotlb yet");
+ return -EINVAL;
+ }
+
if (new & IOMMU_NOTIFIER_MAP) {
error_setg(errp,
"device %02x.%02x.%x requires iommu MAP notifier which is "
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 28c7d781721..6e17d631f77 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -704,6 +704,7 @@ static void vhost_iommu_region_add(MemoryListener *listener,
Int128 end;
int iommu_idx;
IOMMUMemoryRegion *iommu_mr;
+ int ret;
if (!memory_region_is_iommu(section->mr)) {
return;
@@ -726,8 +727,16 @@ static void vhost_iommu_region_add(MemoryListener
*listener,
iommu->iommu_offset = section->offset_within_address_space -
section->offset_within_region;
iommu->hdev = dev;
- memory_region_register_iommu_notifier(section->mr, &iommu->n,
- &error_fatal);
+ ret = memory_region_register_iommu_notifier(section->mr, &iommu->n, NULL);
+ if (ret) {
+ /*
+ * Some vIOMMUs do not support dev-iotlb yet. If so, try to use the
+ * UNMAP legacy message
+ */
+ iommu->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
+ memory_region_register_iommu_notifier(section->mr, &iommu->n,
+ &error_fatal);
+ }
QLIST_INSERT_HEAD(&dev->iommu_list, iommu, iommu_next);
/* TODO: can replay help performance here? */
}
diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index 6b9ef7f6b2b..c2883a2f6c8 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -893,6 +893,11 @@ static int
virtio_iommu_notify_flag_changed(IOMMUMemoryRegion *iommu_mr,
IOMMUNotifierFlag new,
Error **errp)
{
+ if (new & IOMMU_NOTIFIER_DEVIOTLB_UNMAP) {
+ error_setg(errp, "Virtio-iommu does not support dev-iotlb yet");
+ return -EINVAL;
+ }
+
if (old == IOMMU_NOTIFIER_NONE) {
trace_virtio_iommu_notify_flag_add(iommu_mr->parent_obj.name);
} else if (new == IOMMU_NOTIFIER_NONE) {