From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Jann Horn <jannh@google.com>, Eric Biggers <ebiggers3@gmail.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
"Serge E. Hallyn" <serge@hallyn.com>,
arozansk@redhat.com, Davidlohr Bueso <dave@stgolabs.net>,
Manfred Spraul <manfred@colorfullife.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
"x86@kernel.org" <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
"David S. Miller" <davem@davemloft.net>,
Rik van Riel <riel@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection
Date: Mon, 24 Jul 2017 10:44:55 +0200 [thread overview]
Message-ID: <20170724084455.o5asa55fckgyjri2@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87zibujq5t.fsf@concordia.ellerman.id.au>
On Mon, Jul 24, 2017 at 04:38:06PM +1000, Michael Ellerman wrote:
> What I'm not entirely clear on is what the best trade off is in terms of
> overhead vs checks. The summary of behaviour between the fast and full
> versions you promised Ingo will help there I think.
That's something that's probably completely different for PPC than it is
for x86. Both because your primitive is LL/SC and thus the saturation
semantics we need a cmpxchg loop for are more natural in your case
anyway, and the fact that your LL/SC is horrendously slow in any case.
Also, I still haven't seen an actual benchmark where our cmpxchg loop
actually regresses anything, just a lot of yelling about potential
regressions :/
next prev parent reply other threads:[~2017-07-24 8:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-19 0:03 [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook
2017-07-19 0:03 ` [PATCH v6 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook
2017-07-19 0:03 ` [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook
2017-07-19 19:37 ` Josh Poimboeuf
2017-07-19 19:45 ` Kees Cook
2017-07-19 19:52 ` Josh Poimboeuf
2017-07-19 22:50 ` Kees Cook
2017-07-19 23:01 ` Josh Poimboeuf
2017-07-19 23:12 ` Kees Cook
2017-07-19 23:30 ` Josh Poimboeuf
2017-07-20 9:11 ` [PATCH v6 0/2] x86: " Ingo Molnar
2017-07-20 17:15 ` Kees Cook
2017-07-20 22:53 ` Kees Cook
2017-07-21 7:50 ` Ingo Molnar
2017-07-21 21:22 ` Andrew Morton
2017-07-22 3:33 ` Kees Cook
2017-07-24 6:38 ` Michael Ellerman
2017-07-24 8:44 ` Peter Zijlstra [this message]
2017-07-24 12:09 ` Michael Ellerman
2017-07-24 12:23 ` Peter Zijlstra
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