linux-kernel - Re: [RFC v2 2/2] x86, efi: Early use of boot service memory

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Date:	Thu, 21 Nov 2013 23:19:40 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Jerry Hoemann <jerry.hoemann@...com>
Cc:	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, matt.fleming@...el.com,
	yinghai@...nel.org, akpm@...ux-foundation.org, bp@...e.de,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org, penberg@...nel.org,
	mingo.kernel.org@...il.com, vgoyal@...hat.com
Subject: Re: [RFC v2 2/2] x86, efi: Early use of boot service memory

On Thu, Nov 21, 2013 at 02:01:26PM -0700, Jerry Hoemann wrote:
> Some platform have firmware that violate the UEFI spec and access boot service
> code or data segments after the system has called ExitBootServices().
> The call to efi_reserve_boot_services is a workaround to avoid using
> boot service memory until after the kernel has done SetVirtualAddressMap().
> However, this reservation fragments memory which can cause
> large allocations early in boot (e.g. crash kernel) to fail.
> 
> When reserve_crashkernel fails, kdump is disabled.
> 
> This patch creates a quirk list that governs when the workaround,
> efi_reserve_boot_services, is called.
> 
> For all firmware released prior to 2014, the workaround will be
> called unless an entry for the platform is in the quirk list saying
> not to do the workaround.
> 
> For all firmware released 2014 and later,  the workaround will not
> be called unless an entry for the platform is in the quirk list
> saying to call the workaround.

This is yet another quirk list which can grow uncontrolled considering
the notoriety of firmware bugs. And since detecting such spec violation
is very simple - boot Linux on the machine - we should rather disable
this by default for FW >= 2014 and make this test part of the firmware
test suite so that vendors can get a chance to fix their BIOSen.

Provided vendors do boot fwts on their validation platforms, that is.

Yo Fleming, got a better idea? :)

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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