Re: Xen 4.0 crashes with pvops kernel

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> >>> Dom0 to map the IO-APIC space read-only? Perhaps even
.. snip
> Actually, that's a difference to non-pv-ops that I strongly
> believe should be fixed: While in the traditional kernel
> __direct_remap_pfn_range() is used to establish I/O memory
> mappings (and hence there is a way to propagate errors), the
> pv-ops kernel appears to use ioremap_page_range() - just like
> native - which can only return -ENOMEM (upon page table
> allocation failure), due to the lack of a return value from
> set_pte_at().
> 
> But then again I must be missing something here, since
> xen_set_pte_at() falls back to xen_set_pte() if the hypercall
> it tries first fails, and that one would fault when establishing
> the mapping, not when trying to first use it. Jeremy?

Take a look at xen_set_fixmap, which I think is used for most of those
special addresses. It is mapped to a null-space for the IO APIC
addresses.