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

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Message-Id: <5332E2B9020000780000255D@nat28.tlf.novell.com>
Date:	Wed, 26 Mar 2014 13:22:49 +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 14:00, <matt@...sole-pimps.org> wrote:
> On Tue, 25 Mar, at 09:57:54PM, Daniel Kiper wrote:
>> Call efi_memblock_x86_reserve_range() on native EFI platform only.
>> This is not needed and even it should not be called on platforms
>> which wraps EFI infrastructure like Xen.
>> 
>> Signed-off-by: Daniel Kiper <daniel.kiper@...cle.com>
>> ---
>>  arch/x86/kernel/setup.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index ce72964..992b67a 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -933,7 +933,7 @@ void __init setup_arch(char **cmdline_p)
>>  		set_bit(EFI_64BIT, &x86_efi_facility);
>>  	}
>>  
>> -	if (efi_enabled(EFI_BOOT))
>> +	if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature, "EL", 2))
>>  		efi_memblock_x86_reserve_range();
>>  #endif
> 
> 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.

Jan

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