linux-kernel - Re: [PATCH] x86-64, espfix: consider IRQs are off when initializing

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Message-ID: <53C7F6CB.4070606@zytor.com>
Date:	Thu, 17 Jul 2014 09:16:11 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64, espfix: consider IRQs are off when initializing

On 07/17/2014 08:58 AM, Sasha Levin wrote:
> 
> This is the result of getting an error message for allocating with GFP_KERNEL
> saying that we can't do that with IRQs off.
> 
> My assumption after that was that we're not going to be sleeping at all, which
> is why spinlock/GFP_ATOMIC would be correct here.
> 

So we have a problem, but the proposed solution is wrong.  This is
messy... we need this code to be successfully executed before we can
safely schedule *user space* on that processor, but there is no
requirement that we execute it before we enable *interrupts* on that
processor, so maybe there is a way we can fulfill those requirements.

The alternative would be to fail to enable the processor or going into a
spin loop, but either of those would been rather toxic to me.

	-hpa

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