linux-kernel - Re: [PATCH] Add a text

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Message-ID: <528D22DB.1020208@zytor.com>
Date:	Wed, 20 Nov 2013 13:00:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Add a text_poke syscall

On 11/20/2013 09:25 AM, Andi Kleen wrote:
> "H. Peter Anvin" <hpa@...or.com> writes:
>>
>> We're talking user space here, which has different requirement (COW,
>> memory protection, ...) which means it is not really the same code.  You
>> can't take a page fault while patching the kernel.
> 
> The syscall pins the page, then it calls the kernel code.
> There are no page faults during patching.
> 

But you don't need to pin anything if you just do it in userspace.
Again, it is particularly poignant for large batched operations.

	-hpa

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