linux-kernel - Re: [RFC PATCH] x86, espfix: use spin

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Message-ID: <555A40C9.6010605@kernel.org>
Date:	Mon, 18 May 2015 12:43:05 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>
CC:	Borislav Petkov <bp@...en8.de>, Gu Zheng <guz.fnst@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [RFC PATCH] x86, espfix: use spin_lock rather than mutex

On 05/15/2015 12:27 AM, H. Peter Anvin wrote:
> On 05/14/2015 11:54 PM, Ingo Molnar wrote:
>>
>> The only slightly subtle detail with that is to use alloc_pages_node()
>> with the secondary CPU's node, to make sure the espfix stack is
>> NUMA-local to the CPU that is going to use it.
>>
>
> It doesn't hurt, although it isn't super critical as each page will be
> shared among 64 CPUs.  The whole espfix stack is only a single cacheline
> long.
>

I don't think we actually need these pages allocated until we try to run 
user code.  Can we move this very late in initialization instead?

--Andy

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