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Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release

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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?

	Arnd
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[PATCH v2 6/6] vfio: platform: move get/put reset at open/release Eric Auger <eric.auger@linaro.org> - 2015-10-22 11:50 +0200
  Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Arnd Bergmann <arnd@arndb.de> - 2015-10-22 12:30 +0200
    Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Eric Auger <eric.auger@linaro.org> - 2015-10-22 13:50 +0200
      Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Arnd Bergmann <arnd@arndb.de> - 2015-10-22 14:10 +0200
        Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Eric Auger <eric.auger@linaro.org> - 2015-10-22 14:30 +0200
    Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Eric Auger <eric.auger@linaro.org> - 2015-10-22 15:30 +0200
      Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Arnd Bergmann <arnd@arndb.de> - 2015-10-22 16:20 +0200
        Re: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release Eric Auger <eric.auger@linaro.org> - 2015-10-22 16:30 +0200
          Re: [PATCH v2 6/6] vfio: platform: move get/put reset at  open/release Alex Williamson <alex.williamson@redhat.com> - 2015-10-22 17:50 +0200

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