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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 11 Jul 2012 10:04:52 +1000
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Subject: Re: [Qemu-devel] [PATCH 2/2] vfio-powerpc: added VFIO support
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To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org, Alex Williamson <alex.williamson@redhat.com>, qemu-ppc@nongnu.org, Scott Wood <scottwood@freescale.com>, David Gibson <david@gibson.dropbear.id.au>

On Wed, 2012-07-11 at 09:55 +1000, Alexey Kardashevskiy wrote:
> On 11/07/12 08:26, Scott Wood wrote:
> > On 07/10/2012 12:51 AM, Alexey Kardashevskiy wrote:
> >> The patch enables VFIO on POWER.
> >>
> >> It literally does the following:
> >>
> >> 1. POWERPC IOMMU support (the kernel counterpart is required)
> > [snip]
> >> +/* -------- API for POWERPC IOMMU -------- */
> >> +
> >> +#define POWERPC_IOMMU           2
> >> +
> >> +struct tce_iommu_info {
> >> +    __u32 argsz;
> >> +    __u32 dma32_window_start;
> >> +    __u32 dma32_window_size;
> >> +};
> >> +
> >> +#define POWERPC_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
> > 
> > Is there a more specific name that could be used for this?  Not all
> > PowerPC chips have the same kind of IOMMU.

> 
> Ben, is is SPAPR? BOOK3S?

So we have varieties of different iommus in the kernel indeed, we
probably want the info ioctl to reflect that. I would call this one
spapr_tce.

Also we will want a few other things, dunno if that's reflected here,
or whether the ioctl is easily extendable, but in the long run we will
need:

 - Ways to tell KVM about association between a liobn (logical bus
number as used in H_PUT_TCE) and an iommu so we can implement the real
mode H_PUT_TCE properly.

 - We will need some conduit to implement the "DDW" APIs (part of PAPR
allowing the guest to control the DMA windows, ie, by creating new
windows in 64-bit DMA space, with different page sizes etc....). So you
may want to make it clear that the above provides information about the
"base window" specifically.

Cheers,
Ben.