On 11/8/22 04:09, Jason Wang wrote: > 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? OK I will look at this alternative > >> BTW vhost_init_device_iotlb gets enabled parameter but ignores >> it, we really should drop that. > Yes. Yes I saw that too. I will send a patch. > >> 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. OK Thanks Eric > > Thanks > >> >>>> >>>>> -- >>>>> 2.37.3
