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? Thanks Eric > > Arnd > -- 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
