From: Jiri Slaby <jslaby@suse.cz>
To: Thomas Gleixner <tglx@linutronix.de>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>
Cc: "Li, Aubrey" <aubrey.li@linux.intel.com>,
Daniel Drake <drake@endlessm.com>,
"x86@kernel.org" <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Endless Linux Upstreaming Team <linux@endlessm.com>
Subject: Re: [PATCH] x86/apic: Handle missing global clockevent gracefully
Date: Fri, 9 Aug 2019 14:59:04 +0200 [thread overview]
Message-ID: <b7c3809f-cdea-03f0-09f8-a47e6f304ec1@suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.21.1908091443030.21433@nanos.tec.linutronix.de>
On 09. 08. 19, 14:54, Thomas Gleixner wrote:
> Some newer machines do not advertise legacy timers. The kernel can handle
> that situation if the TSC and the CPU frequency are enumerated by CPUID or
> MSRs and the CPU supports TSC deadline timer. If the CPU does not support
> TSC deadline timer the local APIC timer frequency has to be known as well.
>
> Some Ryzens machines do not advertize legacy timers, but there is no
> reliable way to determine the bus frequency which feeds the local APIC
> timer when the machine allows overclocking of that frequency.
>
> As there is no legacy timer the local APIC timer calibration crashes due to
> a NULL pointer dereference when accessing the not installed global clock
> event device.
>
> Switch the calibration loop to a non interrupt based one, which polls
> either TSC (frequency known) or jiffies. The latter requires a global
> clockevent. As the machines which do not have a global clockevent installed
> have a known TSC frequency this is a non issue. For older machines where
> TSC frequency is not known, there is no known case where the legacy timers
> do not exist as that would have been reported long ago.
>
> Reported-by: Daniel Drake <drake@endlessm.com>
> Reported-by: Jiri Slaby <jslaby@suse.cz>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>
> Note: Only lightly tested, but of course not on an affected machine.
Thanks, I will make them test the patch and let you know.
--
js
suse labs
next prev parent reply other threads:[~2019-08-09 12:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-01 6:24 setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 7:16 ` Aubrey Li
2019-08-01 7:35 ` Thomas Gleixner
2019-08-01 7:56 ` Aubrey Li
2019-08-01 8:13 ` Thomas Gleixner
2019-08-01 8:21 ` Li, Aubrey
2019-08-01 10:13 ` Thomas Gleixner
2019-08-01 15:44 ` Lendacky, Thomas
2019-08-08 20:36 ` Thomas Gleixner
2019-08-08 21:01 ` Lendacky, Thomas
2019-08-08 21:08 ` Thomas Gleixner
2019-08-08 21:36 ` Lendacky, Thomas
2019-08-09 12:54 ` [PATCH] x86/apic: Handle missing global clockevent gracefully Thomas Gleixner
2019-08-09 12:59 ` Jiri Slaby [this message]
2019-08-09 13:58 ` Lendacky, Thomas
2019-08-09 19:40 ` Thomas Gleixner
2019-08-12 6:16 ` Daniel Drake
2019-08-12 7:03 ` Jiri Slaby
2019-08-15 5:02 ` Daniel Drake
2019-08-12 7:46 ` Li, Aubrey
2019-08-12 12:24 ` Thomas Gleixner
2019-08-12 12:59 ` Aubrey Li
2019-08-12 17:11 ` Thomas Gleixner
2019-08-19 10:37 ` [tip:x86/urgent] " tip-bot for Thomas Gleixner
2019-08-01 9:00 ` setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 10:17 ` Thomas Gleixner
2019-08-01 7:27 ` Thomas Gleixner
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