Re: [Xen-devel] [PATCH RFC 26/35] arm : acpi read mmio tables from uefi

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Stefano,

On 06/02/2015 22:17, Stefano Stabellini wrote:
> On Fri, 6 Feb 2015, Julien Grall wrote:
> > On 06/02/2015 00:34, Stefano Stabellini wrote:
> > > > diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> > > > index 93c8a8a..930746b 100644
> > > > --- a/xen/arch/arm/setup.c
> > > > +++ b/xen/arch/arm/setup.c
> > > > @@ -50,6 +50,7 @@
> > > >    #include <asm-arm/cputype.h>
> > > >
> > > >    struct bootinfo __initdata bootinfo;
> > > > +struct meminfo __initdata acpi_mmio;
> > > >
> > > >    struct cpuinfo_arm __read_mostly boot_cpu_data;
> > > >
> > > > diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
> > > > index ba5a67d..5ea9ed6 100644
> > > > --- a/xen/include/asm-arm/setup.h
> > > > +++ b/xen/include/asm-arm/setup.h
> > > > @@ -46,6 +46,7 @@ struct bootinfo {
> > > >    };
> > > >
> > > >    extern struct bootinfo bootinfo;
> > > > +extern struct meminfo acpi_mmio;
> > > It might make sense to reuse bootinfo.mem.
> > Do you mean by extending the meminfo structure with a flags indicating if it's
> > a RAM or MMIO range?
> Right.  We could avoid introducing acpi_mmio and instead storing the
> banks info in bootinfo.mem, that I am guessing it would be unused on
> acpi?
It's used by EFI to store the memory bank. So we can't reuse it for 
another purpose.
But we could extend the structure to add a type.

Although, let's wait until we know if we can use UEFI to get the MMIO 
region.
> > I guess it might be good, but I'm concerned about the static size of the
> > array, 64 may not be suffisant.
> Yes, you are right about that.  Do we have any ideas on how many banks
> are available on a few real systems?
I have no ideas.

> The alternative would be to create a list.
At that time, we can't use the boot allocator (memory has not been 
populate). We would have to use the AllocatePages().
Regards,

--
Julien Grall

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