On Tue, Nov 8, 2022 at 7:06 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Mon, Nov 07, 2022 at 10:10:06PM +0100, Eric Auger wrote: > > Hi Michael, > > On 11/7/22 21:42, Michael S. Tsirkin wrote: > > > On Mon, Nov 07, 2022 at 09:34:31PM +0100, Eric Auger wrote: > > >> When the vhost iotlb is used along with a guest virtual iommu > > >> and the guest gets rebooted, some MISS messages may have been > > >> recorded just before the reboot and spuriously executed by > > >> the virtual iommu after the reboot. Despite the device iotlb gets > > >> re-initialized, the messages are not cleared. Fix that by calling > > >> vhost_clear_msg() at the end of vhost_init_device_iotlb(). > > >> > > >> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx> > > >> --- > > >> drivers/vhost/vhost.c | 1 + > > >> 1 file changed, 1 insertion(+) > > >> > > >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > >> index 40097826cff0..422a1fdee0ca 100644 > > >> --- a/drivers/vhost/vhost.c > > >> +++ b/drivers/vhost/vhost.c > > >> @@ -1751,6 +1751,7 @@ int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled) > > >> } > > >> > > >> vhost_iotlb_free(oiotlb); > > >> + vhost_clear_msg(d); > > >> > > >> return 0; > > >> } > > > Hmm. Can't messages meanwhile get processes and affect the > > > new iotlb? > > Isn't the msg processing stopped at the moment this function is called > > (VHOST_SET_FEATURES)? > > > > Thanks > > > > Eric > > It's pretty late here I'm not sure. You tell me what prevents it. So the proposed code assumes that Qemu doesn't process device IOTLB before VHOST_SET_FEAETURES. Consider there's no reset in the general vhost uAPI, I wonder if it's better to move the clear to device code like VHOST_NET_SET_BACKEND. So we can clear it per vq? > > BTW vhost_init_device_iotlb gets enabled parameter but ignores > it, we really should drop that. Yes. > > Also, it looks like if features are set with VIRTIO_F_ACCESS_PLATFORM > and then cleared, iotlb is not properly cleared - bug? Not sure, old IOTLB may still work. But for safety, we need to disable device IOTLB in this case. Thanks > > > > > > > > > > >> -- > > >> 2.37.3 >
