From: Andi Kleen <ak@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>,
dwmw@amazon.co.uk, pjt@google.com, linux-kernel@vger.kernel.org,
gregkh@linux-foundation.org, tim.c.chen@linux.intel.com,
dave.hansen@intel.com, tglx@linutronix.de, luto@amacapital.net
Subject: Re: [PATCH] x86/retpoline: Avoid return buffer underflows on context switch
Date: Mon, 8 Jan 2018 14:25:12 -0800 [thread overview]
Message-ID: <20180108222512.GC6718@tassilo.jf.intel.com> (raw)
In-Reply-To: <20180108221121.GU29822@worktop.programming.kicks-ass.net>
> So pjt did alignment, a single unroll and per discussion earlier today
> (CET) or late last night (PST), he only does 16.
I used the Intel recommended sequence, which recommends 32.
Not sure if alignment makes a difference. I can check.
> Why is none of that done here? Also, can we pretty please stop using
> those retarded number labels, they make this stuff unreadable.
Personally I find the magic labels with strange ASCII characters
far less readable than a simple number.
But can change it if you insist.
> Also, pause is unlikely to stop speculation, that comment doesn't make
> sense. Looking at PJT's version there used to be a speculation trap in
> there, but I can't see that here.
My understanding is that it stops speculation. But could also
use LFENCE.
-Andi
next prev parent reply other threads:[~2018-01-08 22:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-08 20:15 [PATCH] x86/retpoline: Avoid return buffer underflows on context switch Andi Kleen
2018-01-08 21:38 ` David Woodhouse
2018-01-08 22:54 ` Andi Kleen
2018-01-08 22:11 ` Peter Zijlstra
2018-01-08 22:17 ` Woodhouse, David
2018-01-08 22:26 ` Peter Zijlstra
2018-01-08 23:25 ` Woodhouse, David
2018-01-08 22:25 ` Andi Kleen [this message]
2018-01-08 22:58 ` Andi Kleen
2018-01-09 0:15 ` Paul Turner
2018-01-09 0:15 ` Paul Turner
2018-01-09 0:44 ` Woodhouse, David
2018-01-09 0:48 ` David Woodhouse
2018-01-09 2:48 ` Paul Turner
2018-01-09 3:05 ` David Woodhouse
2018-01-12 11:15 ` David Laight
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