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From: Florian Weimer <fweimer@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	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>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	devel@linuxdriverproject.org,
	virtualization@lists.linux-foundation.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	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, 14 Sep 2018 15:06:46 +0200	[thread overview]
Message-ID: <63a0f67d-fdb1-e2fc-5d4d-4f3cfbf86fd1@redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1809141459530.10480@nanos.tec.linutronix.de>

On 09/14/2018 03:05 PM, Thomas Gleixner wrote:
> On Fri, 14 Sep 2018, Florian Weimer wrote:
> 
>> On 09/14/2018 02:50 PM, Thomas Gleixner wrote:
>>> Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime()
>>> implementation, which extended the clockid switch case and added yet
>>> another slightly different copy of the same code.
>>>
>>> Especially the extended switch case is problematic as the compiler tends to
>>> generate a jump table which then requires to use retpolines.
>>
>> Does vDSO code really have to use retpolines?  It's in userspace, after all.
> 
> Unless you have IBRS/STIPB enabled, you need user space ratpoutine as well.

I don't think this is a consensus position, and it obviously depends on 
the (sub)architecture.

Thanks,
Florian


  reply	other threads:[~2018-09-14 13:06 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 [this message]
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
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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