linux-kernel - Re: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from userspace

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Message-ID: <20141117200354.GB25157@pd.tnic>
Date:	Mon, 17 Nov 2014 21:03:54 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from
 userspace

On Mon, Nov 17, 2014 at 11:57:22AM -0800, Andy Lutomirski wrote:
> Would it be worth making a decision on task_work_add vs. stack
> switching first?

Probably a prudent thing to do in order to save unnecessary cycles :-)

> Stack switching pros: all this lockless allocation stuff is completely
> unnecessary, and it's plausible that the stack switching code will be
> added anyway.

Yes.

However, I'd like to be very sure this thing doesn't introduce any
regressions to the MCA code. So even if Tony's testing passes, I'd like
to be very conservative here and stress it more than usual. Because once
this thing hits upstream and stuff starts breaking, it'll be a serious
PITA reverting it.

I hope you can understand my concerns.

Btw, which branch has your latest version - I'd like to take a look at
it in detail.

> task_work_add pros: conceptually simpler mce.c diff.

Right, that's the safe path.

Thanks.

-- 
Regards/Gruss,
    Boris.

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