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

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Date:	Wed, 26 Mar 2014 13:39:42 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Matt Fleming" <matt@...sole-pimps.org>
Cc:	<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>,
	"Daniel Kiper" <daniel.kiper@...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 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.

Jan

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