Hi,
On 1/21/25 9:31 AM, Laurent Vivier wrote: > On 20/01/2025 18:33, Eric Auger wrote: >> When a guest exposed with a vhost device and protected by an >> intel IOMMU gets rebooted, we sometimes observe a spurious warning: >> >> Fail to lookup the translated address ffffe000 >> >> We observe that the IOMMU gets disabled through a write to the global >> command register (CMAR_GCMD.TE) before the vhost device gets stopped. >> When this warning happens it can be observed an inflight IOTLB >> miss occurs after the IOMMU disable and before the vhost stop. In >> that case a flat translation occurs and the check in >> vhost_memory_region_lookup() fails. >> >> Let's disable the IOTLB callbacks when all IOMMU MRs have been >> unregistered. >> >> Signed-off-by: Eric Auger <eric.au...@redhat.com> >> --- >> hw/virtio/vhost.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c >> index 6aa72fd434..128c2ab094 100644 >> --- a/hw/virtio/vhost.c >> +++ b/hw/virtio/vhost.c >> @@ -931,6 +931,10 @@ static void >> vhost_iommu_region_del(MemoryListener *listener, >> break; >> } >> } >> + if (QLIST_EMPTY(&dev->iommu_list) && >> + dev->vhost_ops->vhost_set_iotlb_callback) { >> + dev->vhost_ops->vhost_set_iotlb_callback(dev, false); >> + } >> } >> void vhost_toggle_device_iotlb(VirtIODevice *vdev) > > I think you need the counterpart in vhost_iommu_region_del() (for > instance if we have an add after a del that results in an empty list). > But you cannot unconditionally enable it (for instance if vhost is not > started) if we enter vhost_iommu_region_add(), this means that the iommu_listener has been registered in vhost_vdev_start() and thus vdev->vhost_started is set. > > Perhaps you should move the vhost_set_iotlb_callback() call from > vhost_start()/vhost_stop() to > vhost_iommu_region_add()/vhost_iommu_region_del()? I currently fail to understand whether we shouldn't keep listening to iotlb callbacks when the IOMMU gets disabled. In that case shouldn't we flush the kernel IOTLB and update the hdev->mem->regions to reflect the IOMMR MR disablement? Thanks Eric > > Thanks, > Laurent >