Virtualization - Nov 2022 - [RFC] vhost: Clear the pending messages on vhost_init_device_iotlb()

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 at redhat.com>
> ---
>  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?

> -- 
> 2.37.3

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 at redhat.com>
>> ---
>>  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
>
>
>> -- 
>> 2.37.3