From: Jakub Jelinek <jakub@redhat.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Stephane Eranian <eranian@google.com>,
linux-kernel@vger.kernel.org, tony.luck@intel.com,
reinette.chatre@intel.com, fenghua.yu@intel.com,
peternewman@google.com, james.morse@arm.com, babu.moger@amd.com,
ananth.narayan@amd.com, vschneid@redhat.com,
Nathan Chancellor <nathan@kernel.org>,
clang-built-linux <llvm@lists.linux.dev>,
Borislav Petkov <bp@alien8.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-toolchains@vger.kernel.org
Subject: Re: [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in
Date: Tue, 7 Mar 2023 21:43:30 +0100 [thread overview]
Message-ID: <ZAeh8g0nr3IFRSVI@tucnak> (raw)
In-Reply-To: <20230307184315.GS25951@gate.crashing.org>
On Tue, Mar 07, 2023 at 12:43:16PM -0600, Segher Boessenkool wrote:
> On Tue, Mar 07, 2023 at 12:35:45PM +0100, Peter Zijlstra wrote:
> > So per that summary, I'm going to nit-pick and state we very much want
> > CSE. CSE good. What we don't want it violating store-load ordering.
>
> So you need to describe exactly what you *do* want. There is no way to
> forbid most otherwise valid things. But you can express pretty much all
> dependencies.
>
> > Oh, geez, what a twisty tale that... So Linus knew back in '09 that "p"
> > was icky, but it sorta was the only thing and it 'worked' -- until now
> > :/
>
> The "p" constraint is just like any other address_constraint, in most
> aspects. Since this is very specific to "p", that limits what is going
> on to really just one thing.
Are we actually talking here about "p" constraint or about p/P (x86) modifiers
(asm ("%p0" : : "i" (42));)?
Jakub
next prev parent reply other threads:[~2023-03-07 20:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-03 23:11 [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in Stephane Eranian
2023-03-03 23:17 ` Luck, Tony
2023-03-06 12:01 ` Peter Zijlstra
2023-03-07 0:16 ` Nick Desaulniers
2023-03-07 21:56 ` Bill Wendling
2023-03-07 11:35 ` Peter Zijlstra
2023-03-07 17:48 ` Linus Torvalds
2023-03-07 18:43 ` Segher Boessenkool
2023-03-07 20:43 ` Jakub Jelinek [this message]
2023-03-07 20:54 ` Linus Torvalds
2023-03-07 21:06 ` Linus Torvalds
2023-03-07 21:35 ` Luck, Tony
2023-03-07 21:58 ` Nick Desaulniers
2023-03-08 6:13 ` Stephane Eranian
2023-03-08 23:25 ` Linus Torvalds
2023-03-08 16:02 ` Moger, Babu
2023-03-07 21:11 ` Luck, Tony
2023-03-07 21:14 ` Linus Torvalds
2023-03-07 21:23 ` Luck, Tony
2023-03-08 0:36 ` Luck, Tony
2023-03-07 21:16 ` Nick Desaulniers
2023-03-07 21:19 ` Linus Torvalds
2023-03-07 21:22 ` Nick Desaulniers
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