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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


  reply	other threads:[~2023-03-07 20:44 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20230303231133.1486085-1-eranian@google.com>
     [not found] ` <20230306120106.GE1267364@hirez.programming.kicks-ass.net>
     [not found]   ` <CAKwvOdnRvd5KK01awAyeyt5S36TPPW4_8Z6YL1r4gB-pBrHTbg@mail.gmail.com>
2023-03-07 11:35     ` [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in 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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