> -----Original Message----- > From: Peter Zijlstra [mailto:peterz@xxxxxxxxxxxxx] > Sent: Friday, August 21, 2015 7:34 AM > To: mingo@xxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; > tglx@xxxxxxxxxxxxx; hpa@xxxxxxxxx; vkuznets@xxxxxxxxxx; KY Srinivasan > <kys@xxxxxxxxxxxxx>; torvalds@xxxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx > Cc: linux-tip-commits@xxxxxxxxxxxxxxx > Subject: Re: [tip:x86/platform] x86/hyperv: Mark the Hyper-V TSC as > unstable > > On Fri, Aug 21, 2015 at 12:45:50AM -0700, tip-bot for Vitaly Kuznetsov wrote: > > Commit-ID: 88c9281a9fba67636ab26c1fd6afbc78a632374f > > Gitweb: > https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fgit.kern > el.org%2ftip%2f88c9281a9fba67636ab26c1fd6afbc78a632374f&data=01%7c01 > %7ckys%40microsoft.com%7cca840f9ebba34958dc9a08d2aa35a6c4%7c72f988 > bf86f141af91ab2d7cd011db47%7c1&sdata=hzE233wXaLAYShWPE18SQJQvQe > JguAdB6oj%2bF%2blx7Ok%3d > > Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > AuthorDate: Wed, 19 Aug 2015 09:54:24 -0700 > > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > > CommitDate: Fri, 21 Aug 2015 08:44:38 +0200 > > > > x86/hyperv: Mark the Hyper-V TSC as unstable > > > > The Hyper-V top-level functional specification states, that > > "algorithms should be resilient to sudden jumps forward or > > backward in the TSC value", this means that we should consider > > TSC as unstable. In some cases tsc tests are able to detect the > > instability, it was detected in 543 out of 646 boots in my > > testing: > > > > Measured 6277 cycles TSC warp between CPUs, turning off TSC clock. > > tsc: Marking TSC unstable due to check_tsc_sync_source failed > > > > This is, however, just a heuristic. On Hyper-V platform there > > are two good clocksources: MSR-based hyperv_clocksource and > > recently introduced TSC page. > > *groan*.. and where are the paravirt ops like pv_time_ops for hyperv to > fix up this mess? We register external clocksource and clockevents devices based on a hypervisor based time source and timers to deal with this issue. Regards, K. Y -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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