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

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Date:	Mon, 14 Sep 2015 11:36:32 +0200
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Shannon Zhao <zhaoshenglong@...wei.com>,
	"shannon.zhao@...aro.org" <shannon.zhao@...aro.org>
Cc:	Daniel Kiper <daniel.kiper@...cle.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Mark Rutland <mark.rutland@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"leif.lindholm@...aro.org" <leif.lindholm@...aro.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"julien.grall@...rix.com" <julien.grall@...rix.com>
Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

(snip some cc's)

On 14 September 2015 at 11:31, Shannon Zhao <zhaoshenglong@...wei.com> wrote:
>
>
> On 2015/9/14 17:09, Ard Biesheuvel wrote:
>> On 14 September 2015 at 10:42, Shannon Zhao <zhaoshenglong@...wei.com> wrote:
>> [..]
>>
>>>
>>> It only needs to apply following patch to fix a bug in Linux kernel when
>>> mapping EFI_MEMORY_RUNTIME memory.
>>>
>>
>> Could you explain why you think efi_virtmap_init() should fail if
>> there are no EFI_MEMORY_RUNTIME regions?
>>
>
> 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.

-- 
Ard.
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