linux-kernel - Re: [PATCH v3 3/5] x86: Call efi_memblock_x86_reserve

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Date:	Wed, 26 Mar 2014 14:48:45 +0100
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	Matt Fleming <matt@...sole-pimps.org>, david.vrabel@...rix.com,
	ian.campbell@...rix.com, stefano.stabellini@...citrix.com,
	jeremy@...p.org, fenghua.yu@...el.com, matt.fleming@...el.com,
	tony.luck@...el.com, x86@...nel.org, tglx@...utronix.de,
	xen-devel@...ts.xenproject.org, boris.ostrovsky@...cle.com,
	konrad.wilk@...cle.com, eshelton@...ox.com, mingo@...hat.com,
	linux-efi@...r.kernel.org, linux-ia64@...r.kernel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH v3 3/5] x86: Call efi_memblock_x86_reserve_range() on
 native EFI platform only

On Wed, Mar 26, 2014 at 01:39:42PM +0000, Jan Beulich wrote:
> >>> On 26.03.14 at 14:31, <matt@...sole-pimps.org> wrote:
> > On Wed, 26 Mar, at 01:22:49PM, Jan Beulich wrote:
> >> >>> On 26.03.14 at 14:00, <matt@...sole-pimps.org> wrote:
> >> >
> >> > This could do with a little bit more explanation. Why is it not
> >> > necessary to mark the EFI memory map that was passed to the kernel as
> >> > reserved in memblock?
> >>
> >> Because that's in memory Dom0 doesn't even see: The EFI memory
> >> map is visible to the hypervisor only.
> >
> > So where does boot_params.efi_info.efi_memmap point?
> >
> > If nowhere (i.e. it's NULL) that's no problem because memblock_reserve()
> > handles zero size regions just fine.
>
> That's a question to Daniel - in our implementation (with a separate
> Xen kernel that can't run on bare hardware) boot_params as a whole
> simply doesn't exist.

On my machine this function crashes on Xen so that is why I have changed
condition. However, if you say that this issue could be solved in
another way I will investigate it further.

Daniel
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