Re: [PATCH 3/3] iommu/virtio: Enable x86 support

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
> > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
> > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
> > > > With the built-in topology description in place, x86 platforms can now
> > > > use the virtio-iommu.
> > > > 
> > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > > > ---
> > > >   drivers/iommu/Kconfig | 3 ++-
> > > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > > index 068d4e0e3541..adcbda44d473 100644
> > > > --- a/drivers/iommu/Kconfig
> > > > +++ b/drivers/iommu/Kconfig
> > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU
> > > >   config VIRTIO_IOMMU
> > > >   	bool "Virtio IOMMU driver"
> > > >   	depends on VIRTIO=y
> > > > -	depends on ARM64
> > > > +	depends on (ARM64 || X86)
> > > >   	select IOMMU_API
> > > > +	select IOMMU_DMA
> > > 
> > > Can that have an "if X86" for clarity? AIUI it's not necessary for
> > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
> > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
> > > right?
> > > 
> > > Robin.
> > 
> > In fact does not this work on any platform now?
> 
> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
> has been converted recently [1] but VT-d still implements its own DMA ops
> (conversion patches are on the list [2]). On Arm the arch Kconfig selects
> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
> complete. Until then I can add a "if X86" here for clarity.
> 
> Thanks,
> Jean
> 
> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/

What about others? E.g. PPC?

-- 
MST