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

[Nataliya Korovkina <malus.brandywine@xxxxxxxxx>]

On Wed, May 6, 2020 at 9:43 AM Boris Ostrovsky
<boris.ostrovsky@xxxxxxxxxx> wrote:
>
>
> On 5/6/20 9:08 AM, Nataliya Korovkina wrote:
> > Hello,
> >
> > What I found out: rpi_firmware_property_list() allocates memory from
> > dma_atomic_pool which was mapped to VMALLOC region, so virt_to_page()
> > is not eligible in this case.
>
>
> So then it seems it didn't go through xen_swiotlb_alloc_coherent(). In
> which case it has no business calling xen_swiotlb_free_coherent().
>
>
> -boris
>
>
>
>

It does go.
dma_alloc_coherent() indirectly calls xen_swiotlb_alloc_coherent(),
then  xen_alloc_coherent_pages() eventually calls arch_dma_alloc() in
remap.c which successfully allocates pages from atomic pool.

The patch Julien offered for domian_build.c moved Dom0 banks in the
first G of RAM.
So it covered the previous symptom (a crash during allocation) because
now we avoid pathway  when we mark a page "XenMapped".

But the symptom still remains in xen_swiotlb_free_coherent() because
"TestPage..." is called unconditionally. virt_to_page() is not
applicable to such allocations.

Thanks,
Nataliya