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 <[email protected]>
> > > ---
> > >   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/[email protected]/
[2] https://lore.kernel.org/linux-iommu/[email protected]/
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