On Thu, 2015-10-22 at 16:23 +0200, Eric Auger wrote: > On 10/22/2015 04:10 PM, Arnd Bergmann wrote: > > On Thursday 22 October 2015 15:26:55 Eric Auger wrote: > >>>> @@ -181,6 +182,8 @@ static int vfio_platform_open(void *device_data) > >>>> if (ret) > >>>> goto err_irq; > >>>> > >>>> + vfio_platform_get_reset(vdev); > >>>> + > >>>> if (vdev->reset) > >>>> vdev->reset(vdev); > >>>> > >>> > >>> This needs some error handling to ensure that the open() fails > >>> if there is no reset handler. > >> > >> Is that really what we want? The code was meant to allow the use case > >> where the VFIO platform driver would be used without such reset module. > >> > >> I think the imperious need for a reset module depends on the device and > >> more importantly depends on the IOMMU mapping. With QEMU VFIO > >> integration this is needed because the whole VM memory is IOMMU mapped > >> but in a simpler user-space driver context, we might live without. > >> > >> Any thought? > > > > I would think we need a reset driver for any device that can start DMA, > > otherwise things can go wrong as soon as you attach it to a different domain > > while there is ongoing DMA. > > > > Maybe we could just allow devices to be attached without a reset handler, > > but then disallow DMA on them? > > Well I am tempted to think that most assigned devices will perform DMA > accesses so to me this somehow comes to the same result, ie disallowing > functional passthrough for devices not properly/fully integrated. > > Alex/Baptiste, any opinion on this? We have an IOMMU and the user doesn't get access to the device until the IOMMU domain is established. So, ideally yes, we should have a way to reset the device, but I don't see it as a requirement. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
