Re: [Xen-devel] Re: [Xen-changelog] [linux-2.6.18-xen] Add "#ifdef ARCH_HAS_DEV_MEM" to archtecture specific file_operations.

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

On Mon, 2007-07-09 at 20:26 +0100, Keir Fraser wrote:
> On 9/7/07 20:20, "Hollis Blanchard" <hollisb@xxxxxxxxxx> wrote:
> 
> >> By the way, I wonder how PPC manages to build both drivers/char/mem.c and
> >> drivers/xen/char/mem.c without ARCH_HAS_DEV_MEM? The model is supposed to 
> >> be
> >> that mem_fops defined by the Xen file is picked up by the generic file. If
> >> !ARCH_HAS_DEV_MEM then that doesn't happen -- so who picks up the Xen
> >> mem_fops? 
> > 
> > Hmmm, yeah. Looks like we haven't tested that... :)
> 
> If you don't need to build both then there is potentially no problem with
> the Xen file hijacking the xlate_dev_mem() functions.

PowerPC Linux builds support for multiple platforms, including multiple
hypervisors, into a single binary (paravirt_ops was inspired by ppc_md).
For the most part our Xen patches continue this model, but because we
don't really test our Xen kernel on non-Xen platforms, there are a
couple bugs that would need fixing.

So compile-time ifdefs for /dev/mem won't work long-term, but I'm not
really worried about it.

-- 
Hollis Blanchard
IBM Linux Technology Center


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