linux-kernel - Re: [PATCHv2 2/4] x86_64: embrace KERNEL_STACK

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Message-ID: <CAK1hOcMgrpw5+Uz+5U25Xq_1fJNTGc4PUtw+YzGGYBZ-YKaJew@mail.gmail.com>
Date:	Wed, 21 Jan 2015 14:44:10 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
Cc:	Andy Lutomirski <luto@...capital.net>, X86 ML <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...e.de>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCHv2 2/4] x86_64: embrace KERNEL_STACK_OFFSET

On Sun, Jan 18, 2015 at 12:45 PM, Alexander van Heukelum
<heukelum@...tmail.fm> wrote:
> KERNEL_STACK_OFFSET is the offset from the top of the kernel stack
> page to the value of the kernel_stack percpu variable. This patch
> changes KERNEL_STACK_OFFSET to configure a reserved space of 16
> bytes above the user ptregs frame. KERNEL_STACK_OFFSET must be
> set to a multiple of 16 bytes due to the automatic stack alignment
> of interrupts, traps, and exceptions on x86_64.

I propose to set kernel_stack percpu variable to point
to the top of kernel stack (obvious, isn't it?)
and eliminate KERNEL_STACK_OFFSET altogether.
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