linux-kernel - Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

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Date:	Mon, 14 Sep 2015 04:39:49 -0600
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Ard Biesheuvel" <ard.biesheuvel@...aro.org>
Cc:	"Mark Rutland" <mark.rutland@....com>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"julien.grall@...rix.com" <julien.grall@...rix.com>,
	"Stefano Stabellini" <stefano.stabellini@...citrix.com>,
	"Shannon Zhao" <zhaoshenglong@...wei.com>,
	"leif.lindholm@...aro.org" <leif.lindholm@...aro.org>,
	"shannon.zhao@...aro.org" <shannon.zhao@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"Daniel Kiper" <daniel.kiper@...cle.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names
 of EFI stub parameters

>>> On 14.09.15 at 11:36, <ard.biesheuvel@...aro.org> wrote:
> On 14 September 2015 at 11:31, Shannon Zhao <zhaoshenglong@...wei.com> wrote:
>> My understanding is that if there are no EFI_MEMORY_RUNTIME regions, it
>> means we can't use runtime services and should not set the bit
>> EFI_RUNTIME_SERVICES of efi.flags. But if efi_virtmap_init() return
>> true, the bit will be set.
>>
> 
> As I said, if you don't want the EFI_RUNTIME_SERVICES bit to be set
> for other reasons, don't rig efi_virtmap_init() to return false when
> it shouldn't.
> 
>>> The absence of such regions is allowed by the spec, so
>>> efi_virtmap_init() is correct imo to return success.
>>>
>> Sorry, not well know about the spec. Could you point out where the spec
>> says this?
>>
> 
> Well, I think it doesn't work that way. You are claiming that a memory
> map without at least one EFI_MEMORY_RUNTIME constitutes an error
> condition, so the burden is on you to provide a reference to the spec
> that says you must have at least one such region.

Sure, from a spec pov you're right. But where would runtime
services code/data live when there's not a single region marked
as needing a runtime mapping. IOW while the spec doesn't say
so, assuming no runtime services when there's not at least one
executable region with the runtime flag set could serve as a stop
gap measure against flawed firmware.

Jan

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