From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Nadav Amit <nadav.amit@gmail.com>, Rik van Riel <riel@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Arjan van de Ven <arjan@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Banman <abanman@sgi.com>, Mike Travis <travis@sgi.com>,
Dimitri Sivanich <sivanich@sgi.com>,
Juergen Gross <jgross@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Mike Travis <mike.travis@hpe.com>,
Dimitri Sivanich <sivanich@hpe.com>,
Andrew Banman <abanman@hpe.com>
Subject: Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking
Date: Thu, 22 Jun 2017 21:05:22 +0200 [thread overview]
Message-ID: <20170622190522.ou2wiyepupiasi2a@pd.tnic> (raw)
In-Reply-To: <CALCETrUA-+9ORRXFrYdyEg5ZQOEbDFrwq4uuRWDb89V49QRBWw@mail.gmail.com>
On Thu, Jun 22, 2017 at 10:47:29AM -0700, Andy Lutomirski wrote:
> I figured that some future reader of this patch might actually want to
> see this text, though.
Oh, don't get me wrong: with commit messages more is more, in the
general case. That's why I said "if".
> >> The UV tlbflush code is rather dated and should be changed.
>
> And I'd definitely like the UV maintainers to notice this part, now or
> in the future :) I don't want to personally touch the UV code with a
> ten-foot pole, but it really should be updated by someone who has a
> chance of getting it right and being able to test it.
Ah, could be because they moved recently and have hpe addresses now.
Lemme add them.
> >> +
> >> + if (cpumask_test_cpu(cpu, mm_cpumask(mm)))
> >> + cpumask_clear_cpu(cpu, mm_cpumask(mm));
> >
> > It seems we haz a helper for that: cpumask_test_and_clear_cpu() which
> > does BTR straightaway.
>
> Yeah, but I'm doing this for performance. I think that all the
> various one-line helpers do a LOCKed op right away, and I think it's
> faster to see if we can avoid the LOCKed op by trying an ordinary read
> first.
Right, the test part of the operation is unlocked so if that is the
likely case, it is a win.
> OTOH, maybe this is misguided -- if the cacheline lives somewhere else
> and we do end up needing to update it, we'll end up first sharing it
> and then making it exclusive, which increases the amount of cache
> coherency traffic, so maybe I'm optimizing for the wrong thing. What
> do you think?
Yeah, but we'll have to do that anyway for the locked operation. Ok,
let's leave it split like it is.
> It did in one particular buggy incarnation. It would also trigger if,
> say, suspend/resume corrupts CR3. Admittedly this is unlikely, but
> I'd rather catch it. Once PCID is on, corruption seems a bit less
> farfetched -- this assertion will catch anyone who accidentally does
> write_cr3(read_cr3_pa()).
Ok, but let's put a comment over it pls as it is not obvious when
something like that can happen.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2017-06-22 19:05 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-21 5:22 [PATCH v3 00/11] PCID and improved laziness Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 01/11] x86/mm: Don't reenter flush_tlb_func_common() Andy Lutomirski
2017-06-21 8:01 ` Thomas Gleixner
2017-06-21 8:49 ` Borislav Petkov
2017-06-21 15:15 ` Andy Lutomirski
2017-06-21 23:26 ` Nadav Amit
2017-06-22 2:27 ` Andy Lutomirski
2017-06-22 7:32 ` Ingo Molnar
2017-06-21 5:22 ` [PATCH v3 02/11] x86/ldt: Simplify LDT switching logic Andy Lutomirski
2017-06-21 8:03 ` Thomas Gleixner
2017-06-21 9:40 ` Borislav Petkov
2017-06-22 11:08 ` [tip:x86/mm] x86/ldt: Simplify the " tip-bot for Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 03/11] x86/mm: Remove reset_lazy_tlbstate() Andy Lutomirski
2017-06-21 8:03 ` Thomas Gleixner
2017-06-21 9:50 ` Borislav Petkov
2017-06-22 11:08 ` [tip:x86/mm] " tip-bot for Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID Andy Lutomirski
2017-06-21 8:05 ` Thomas Gleixner
2017-06-21 10:33 ` Borislav Petkov
2017-06-21 15:23 ` Andy Lutomirski
2017-06-21 17:06 ` Borislav Petkov
2017-06-21 17:43 ` Borislav Petkov
2017-06-22 2:34 ` Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 05/11] x86/mm: Track the TLB's tlb_gen and update the flushing algorithm Andy Lutomirski
2017-06-21 8:32 ` Thomas Gleixner
2017-06-21 15:11 ` Andy Lutomirski
2017-06-21 18:44 ` Borislav Petkov
2017-06-22 2:46 ` Andy Lutomirski
2017-06-22 7:24 ` Borislav Petkov
2017-06-22 14:48 ` Andy Lutomirski
2017-06-22 14:59 ` Borislav Petkov
2017-06-22 15:55 ` Andy Lutomirski
2017-06-22 17:22 ` Borislav Petkov
2017-06-22 18:08 ` Andy Lutomirski
2017-06-23 8:42 ` Borislav Petkov
2017-06-23 15:46 ` Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking Andy Lutomirski
2017-06-21 9:01 ` Thomas Gleixner
2017-06-21 16:04 ` Andy Lutomirski
2017-06-21 17:29 ` Borislav Petkov
2017-06-22 14:50 ` Borislav Petkov
2017-06-22 17:47 ` Andy Lutomirski
2017-06-22 19:05 ` Borislav Petkov [this message]
2017-07-27 19:53 ` Andrew Banman
2017-07-28 2:05 ` Andy Lutomirski
2017-06-23 13:34 ` Boris Ostrovsky
2017-06-23 15:22 ` Andy Lutomirski
2017-06-21 5:22 ` [PATCH v3 07/11] x86/mm: Stop calling leave_mm() in idle code Andy Lutomirski
2017-06-21 9:22 ` Thomas Gleixner
2017-06-21 15:16 ` Andy Lutomirski
2017-06-23 9:07 ` Borislav Petkov
2017-06-21 5:22 ` [PATCH v3 08/11] x86/mm: Disable PCID on 32-bit kernels Andy Lutomirski
2017-06-21 9:26 ` Thomas Gleixner
2017-06-23 9:24 ` Borislav Petkov
2017-06-21 5:22 ` [PATCH v3 09/11] x86/mm: Add nopcid to turn off PCID Andy Lutomirski
2017-06-21 9:27 ` Thomas Gleixner
2017-06-23 9:34 ` Borislav Petkov
2017-06-21 5:22 ` [PATCH v3 10/11] x86/mm: Enable CR4.PCIDE on supported systems Andy Lutomirski
2017-06-21 9:39 ` Thomas Gleixner
2017-06-21 13:40 ` Thomas Gleixner
2017-06-21 20:34 ` Andy Lutomirski
2017-06-23 11:50 ` Borislav Petkov
2017-06-23 15:28 ` Andy Lutomirski
2017-06-23 13:35 ` Boris Ostrovsky
2017-06-21 5:22 ` [PATCH v3 11/11] x86/mm: Try to preserve old TLB entries using PCID Andy Lutomirski
2017-06-21 13:38 ` Thomas Gleixner
2017-06-21 13:40 ` Thomas Gleixner
2017-06-22 2:57 ` Andy Lutomirski
2017-06-22 12:21 ` Thomas Gleixner
2017-06-22 18:12 ` Andy Lutomirski
2017-06-22 21:22 ` Thomas Gleixner
2017-06-23 3:09 ` Andy Lutomirski
2017-06-23 7:29 ` Thomas Gleixner
2017-06-22 16:09 ` Nadav Amit
2017-06-22 18:10 ` Andy Lutomirski
2017-06-26 15:58 ` Borislav Petkov
2017-06-21 18:23 ` [PATCH v3 00/11] PCID and improved laziness Linus Torvalds
2017-06-22 5:19 ` Andy Lutomirski
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