Re: [PATCH v1 10/29] xen/asm-generic: introduce stub header iommu.h

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Thu, 2023-10-19 at 11:44 +0200, Jan Beulich wrote:
> On 14.09.2023 16:56, Oleksii Kurochko wrote:
> > --- /dev/null
> > +++ b/xen/include/asm-generic/iommu.h
> > @@ -0,0 +1,17 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +#ifndef __ASM_GENERIC_IOMMU_H__
> > +#define __ASM_GENERIC_IOMMU_H__
> > +
> > +struct arch_iommu {
> > +};
> > +
> > +#endif /* __ASM_IOMMU_H__ */
> This one's perhaps slightly more "interesting": Yes, we have a
> HAS_PASSTHROUGH Kconfig option, which both Arm and x86 select. But it
> is in principle possible to support guests without any kind of IOMMU
> (permitting solely emulated and PV devices). In which case what's
> (imo) needed here in addition is
> 
> #ifdef CONFIG_HAS_PASSTHROUGH
> # error
> #endif
I am not 100% sure but not all platform has support of IOMMU.

And I thought that passthrough it is when a device is fully committed
to  a guest domain with all MMIO things. So it is a question of
properly mapping MMIO to guest domain. Am I right?

~ Oleksii