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SubjectRe: ACPI early ioremap problems
On Sat, Jan 19, 2008 at 04:30:55PM +0100, Ingo Molnar wrote:
> > > that case it's a 64-bit early_ioremap() bug that we want to find
> > > even if ACPI didnt use early_ioremap().
> > >
> > > and this all runs before zap_low_mappings(), right?
> >
> > No after. Since some time x86-64 does the equivalent of z_l_m() in
> > head64(); this means before start_kernel and definitely before
> > setup_arch which sets up ACPI.
>
> that would mean early_ioremap() should switch to ioremap() after that
> point. Could you try that, does it resolve the failure you are seeing?

ioremap() does alloc_page and that won't work before
paging_init(). Early ACPI scan is before paging_init() because
paging_init() needs node discovery at at least; which requires
some ACPI tables.

> Long-term we want to have a single, uniform ioremap() interface (on
> 32-bit and 64-bit x86 as well) that can be used anytime, which just
> switches to the right lowlevel method depending on how far we are into
> the pagetable and memory subsystem bootstrap - instead of these more
> fragile "can we now use early_ioremap() or should we already be using
> ioremap()" usages.

I didn't think there were enough early/bt_ioremap() users for this
to be really worthwhile. The only code that does both I'm aware of
is the memory setup code.

-Andi



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