From: "Lukas Bulwahn" <lukas.bulwahn@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Lukas Bulwahn <lukas.bulwahn@gmail.com>,
Balbir Singh <sblbir@amazon.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
kernel-janitors@vger.kernel.org, linux-safety@lists.elisa.tech
Subject: Re: [PATCH -next for tip:x86/pti] x86/tlb: drop unneeded local vars in enable_l1d_flush_for_task()
Date: Wed, 30 Sep 2020 18:53:37 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.2009301848050.21555@felia> (raw)
In-Reply-To: <87eemji887.fsf@nanos.tec.linutronix.de>
On Wed, 30 Sep 2020, Thomas Gleixner wrote:
> On Tue, Sep 29 2020 at 10:37, Peter Zijlstra wrote:
> > Here, I fixed it..
>
> Well, no. What Balbir is trying to do here is to establish whether a
> task runs on a !SMT core. sched_smt_active() is system wide, but their
> setup is to have a bunch of SMT enabled cores and cores where SMT is off
> because the sibling is offlined. They affine these processes to non SMT
> cores and the check there validates that before it enabled that flush
> thingy.
>
> Of course this is best effort voodoo because if all CPUs in the mask are
> offlined then the task is moved to a SMT enabled one where L1D flush is
> useless. Though offlining their workhorse CPUs is probably not the daily
> business for obvious raisins.
>
Thanks, Thomas.
So, I will keep the semantics as-is, clean up the patch with
preempt_{dis,en}able() and send out a v2.
Lukas
next prev parent reply other threads:[~2020-09-30 16:53 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 12:44 [PATCH -next for tip:x86/pti] x86/tlb: drop unneeded local vars in enable_l1d_flush_for_task() Lukas Bulwahn
2020-09-28 20:43 ` Nathan Chancellor
2020-09-29 7:12 ` Peter Zijlstra
2020-09-29 8:33 ` Lukas Bulwahn
2020-09-29 8:37 ` Peter Zijlstra
2020-09-30 15:40 ` Thomas Gleixner
2020-09-30 16:53 ` Lukas Bulwahn [this message]
2020-09-30 17:03 ` Peter Zijlstra
2020-09-30 18:00 ` Thomas Gleixner
2020-09-30 18:35 ` Peter Zijlstra
2020-09-30 21:38 ` Thomas Gleixner
2020-09-30 22:59 ` Singh, Balbir
2020-09-30 23:49 ` Singh, Balbir
2020-10-01 0:48 ` Singh, Balbir
2020-10-01 8:17 ` Thomas Gleixner
2020-10-01 8:19 ` Peter Zijlstra
2020-09-30 22:46 ` Singh, Balbir
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