Re: Troubles running Xen on Raspberry Pi 4 with 5.6.1 DomU

[Corey Minyard <minyard@xxxxxxx>]

Snip

> > > > > whether
> > > > > this was already done:
> > > > >      1) Does the kernel boot on baremetal (i.e without Xen)? This 
> > > > > should
> > > > > help
> > > > > to confirm whether the bug is Xen is related.
> > > > 
> > > > Yes it boots
> > > > 
> > > > >      2) Swiotlb should not be necessary for basic dom0 boot on Arm. 
> > > > > Did
> > > > > you try
> > > > > to disable it? This should help to confirm whether swiotlb is the
> > > > > problem or
> > > > > not.
> > > > 
> > > > It boots disabling swiotlb-xen
> > > 
> > > Thank you for the answer! swiotlb-xen should basically be a NOP for dom0. 
> > > So
> > > this suggests swiotlb is doing some transformation on the DMA address.
> > > 
> > > I have an idea what may have gone wrong. AFAICT, xen-swiotlb seems to 
> > > assume
> > > the DMA address space and CPU address space is the same. Is RPI using the
> > > same address space?
> > 
> > Another question, is the DMA request bounced? If so, are we sure the bounce
> > buffer is in the first GB?
> 
> Yes, it is. This is actually where we spent the last few days, and I
> found another little related bug in the initialization of the
> swiotlb-xen but now I am sure the memory is under 1GB (0x34000000-0x38000000)

Was anything ever resolved on this issue?  It just kind of ended for me,
and I looked in the main kernel and didn't find anything that looked
related.

Thanks,

-corey