From: Marcelo Tosatti <mtosatti@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>,
Wanpeng Li <kernellwp@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Matt Rickard <matt@softrans.com.au>,
Stephen Boyd <sboyd@kernel.org>,
John Stultz <john.stultz@linaro.org>,
Florian Weimer <fweimer@redhat.com>,
KY Srinivasan <kys@microsoft.com>,
devel@linuxdriverproject.org,
Linux Virtualization <virtualization@lists.linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>, Juergen Gross <jgross@suse.com>
Subject: Re: [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support
Date: Fri, 5 Oct 2018 18:18:41 -0300 [thread overview]
Message-ID: <20181005211838.GB7129@amt.cnet> (raw)
In-Reply-To: <87k1mycfju.fsf@vitty.brq.redhat.com>
On Thu, Oct 04, 2018 at 09:54:45AM +0200, Vitaly Kuznetsov wrote:
> Marcelo Tosatti <mtosatti@redhat.com> writes:
>
> > On Wed, Oct 03, 2018 at 11:22:58AM +0200, Vitaly Kuznetsov wrote:
> >>
> >> There is a very long history of different (hardware) issues Marcelo was
> >> fighting with and the current code is the survived Frankenstein.
> >
> > Right, the code has to handle different TSC modes.
> >
> >> E.g. it
> >> is very, very unclear what "catchup", "always catchup" and
> >> masterclock-less mode in general are and if we still need them.
> >
> > Catchup means handling exposed (to guest) TSC frequency smaller than
> > HW TSC frequency.
> >
> > That is "frankenstein" code, could be removed.
> >
> >> That said I'm all for simplification. I'm not sure if we still need to
> >> care about buggy hardware though.
> >
> > What simplification is that again?
> >
>
> I was hoping to hear this from you :-) If I am to suggest how we can
> move forward I'd propose:
> - Check if pure TSC can be used on SkyLake+ systems (where TSC scaling
> is supported).
In that case just use TSC clocksource on the guest directly: i am
writing code for that now (its faster than pvclock syscall).
> - Check if non-masterclock mode is still needed. E.g. HyperV's TSC page
> clocksource is a single page for the whole VM, not a per-cpu thing. Can
> we think that all the buggy hardware is already gone?
As Peter mentioned, non sync TSC hardware might exist in the future.
And older hardware must be supported.
next prev parent reply other threads:[~2018-10-05 21:19 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-14 12:50 [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support Thomas Gleixner
2018-09-14 12:50 ` [patch 01/11] clocksource: Provide clocksource_arch_init() Thomas Gleixner
2018-09-14 12:50 ` [patch 02/11] x86/time: Implement clocksource_arch_init() Thomas Gleixner
2018-09-14 15:45 ` Vitaly Kuznetsov
2018-09-15 6:05 ` Thomas Gleixner
2018-09-14 12:50 ` [patch 03/11] x86/vdso: Enforce 64bit clocksource Thomas Gleixner
2018-09-14 12:50 ` [patch 04/11] x86/vdso: Use unsigned int consistently for vsyscall_gtod_data::seq Thomas Gleixner
2018-09-14 12:50 ` [patch 05/11] x86/vdso: Introduce and use vgtod_ts Thomas Gleixner
2018-09-14 12:50 ` [patch 06/11] x86/vdso: Collapse high resolution functions Thomas Gleixner
2018-09-14 12:50 ` [patch 07/11] x86/vdso: Collapse coarse functions Thomas Gleixner
2018-09-14 12:50 ` [patch 08/11] x86/vdso: Replace the clockid switch case Thomas Gleixner
2018-09-14 12:50 ` [patch 09/11] x86/vdso: Simplify the invalid vclock case Thomas Gleixner
2018-09-17 19:25 ` Andy Lutomirski
2018-09-17 20:12 ` John Stultz
2018-09-18 7:52 ` Thomas Gleixner
2018-09-18 8:30 ` Peter Zijlstra
2018-09-18 8:52 ` Thomas Gleixner
2018-09-18 10:06 ` Thomas Gleixner
2018-09-18 10:41 ` Thomas Gleixner
2018-09-18 12:48 ` Peter Zijlstra
2018-09-18 13:23 ` Thomas Gleixner
2018-09-18 13:38 ` Peter Zijlstra
2018-09-18 15:52 ` Thomas Gleixner
2018-09-27 14:41 ` Thomas Gleixner
2018-09-18 14:01 ` Andy Lutomirski
2018-09-18 22:46 ` Thomas Gleixner
2018-09-18 23:03 ` Andy Lutomirski
2018-09-18 23:16 ` Thomas Gleixner
2018-09-27 14:36 ` Thomas Gleixner
2018-09-27 14:39 ` Andy Lutomirski
2018-09-19 9:08 ` Rasmus Villemoes
2018-09-19 13:29 ` Thomas Gleixner
2018-09-14 12:50 ` [patch 10/11] x86/vdso: Move cycle_last handling into the caller Thomas Gleixner
2018-09-14 15:26 ` Vitaly Kuznetsov
2018-09-14 12:50 ` [patch 11/11] x66/vdso: Add CLOCK_TAI support Thomas Gleixner
2018-09-14 14:04 ` Andy Lutomirski
2018-09-14 14:27 ` Thomas Gleixner
2018-09-14 14:59 ` Andy Lutomirski
2018-09-16 9:39 ` Thomas Gleixner
2018-09-14 12:56 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and " Florian Weimer
2018-09-14 13:05 ` Thomas Gleixner
2018-09-14 13:06 ` Florian Weimer
2018-09-14 13:19 ` Thomas Gleixner
2018-09-14 13:09 ` Peter Zijlstra
2018-09-14 14:22 ` Arnd Bergmann
2018-09-17 13:00 ` Thomas Gleixner
2018-09-24 21:08 ` Arnd Bergmann
2018-10-03 5:15 ` Andy Lutomirski
2018-10-03 9:22 ` Vitaly Kuznetsov
2018-10-03 10:20 ` Andy Lutomirski
2018-10-03 12:01 ` Vitaly Kuznetsov
2018-10-03 14:20 ` Andy Lutomirski
2018-10-03 15:10 ` Thomas Gleixner
2018-10-03 16:18 ` Andy Lutomirski
2018-10-03 19:06 ` Marcelo Tosatti
2018-10-04 7:54 ` Vitaly Kuznetsov
2018-10-04 8:11 ` Peter Zijlstra
2018-10-04 14:00 ` Andy Lutomirski
2018-10-04 19:31 ` Peter Zijlstra
2018-10-04 20:05 ` Andy Lutomirski
2018-10-04 22:15 ` Andy Lutomirski
2018-10-06 20:27 ` Marcelo Tosatti
2018-10-06 22:28 ` Andy Lutomirski
2018-10-08 15:26 ` Marcelo Tosatti
2018-10-08 17:38 ` Andy Lutomirski
2018-10-08 19:36 ` Marcelo Tosatti
2018-10-09 20:09 ` Andy Lutomirski
2018-10-11 22:27 ` Marcelo Tosatti
2018-10-11 23:00 ` Andy Lutomirski
2018-10-15 13:39 ` Marcelo Tosatti
2018-10-06 20:49 ` Marcelo Tosatti
2018-10-04 12:00 ` Paolo Bonzini
2018-10-04 14:04 ` Andy Lutomirski
2018-10-05 21:18 ` Marcelo Tosatti [this message]
2018-10-03 19:00 ` Marcelo Tosatti
2018-10-03 19:05 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support\ Marcelo Tosatti
2018-10-03 22:32 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support Andy Lutomirski
2018-10-04 16:37 ` Marcelo Tosatti
2018-10-04 17:08 ` Andy Lutomirski
2018-10-04 17:28 ` Vitaly Kuznetsov
2018-10-04 20:32 ` Andy Lutomirski
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