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

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Message-ID: <55F693F5.8030203@huawei.com>
Date:	Mon, 14 Sep 2015 17:31:33 +0800
From:	Shannon Zhao <zhaoshenglong@...wei.com>
To:	Ard Biesheuvel <ard.biesheuvel@...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>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"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>,
	"freebsd-arm@...ebsd.org" <freebsd-arm@...ebsd.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"jbeulich@...e.com" <jbeulich@...e.com>,
	"peter.huangpeng@...wei.com" <peter.huangpeng@...wei.com>,
	"shannon.zhao@...aro.org" <shannon.zhao@...aro.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters



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.

> 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?

> If you are trying to work around the issue where Xen does not expose
> any Runtime Services regions, there is simply no way to do that and be
> still UEFI compliant. I have suggested before that we should perhaps
> tolerate this anyway, by considering the case where the EFI System
> Table has a NULL runtime services pointer. But rigging
> efi_virtmap_init() like this is really not the way to achieve that.
> 

-- 
Shannon

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