From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Sistare <steven.sistare@oracle.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
linux@armlinux.org.uk,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
John Stultz <john.stultz@linaro.org>,
sboyd@codeaurora.org, x86@kernel.org,
LKML <linux-kernel@vger.kernel.org>,
mingo@redhat.com, "H. Peter Anvin" <hpa@zytor.com>,
douly.fnst@cn.fujitsu.com, Peter Zijlstra <peterz@infradead.org>,
Prarit Bhargava <prarit@redhat.com>,
feng.tang@intel.com, Petr Mladek <pmladek@suse.com>,
gnomes@lxorguk.ukuu.org.uk, linux-s390@vger.kernel.org,
andriy.shevchenko@linux.intel.com, boris.ostrovsky@oracle.com,
pbonzini@redhat.com
Subject: Re: [PATCH v12 09/11] x86/tsc: prepare for early sched_clock
Date: Fri, 29 Jun 2018 04:57:52 -0400 [thread overview]
Message-ID: <20180629085752.zkbxlwc2rzlm63lk@xakep.localdomain> (raw)
In-Reply-To: <alpine.DEB.2.21.1806290925340.1578@nanos.tec.linutronix.de>
On 18-06-29 09:30:10, Thomas Gleixner wrote:
> On Thu, 28 Jun 2018, Pavel Tatashin wrote:
> > On Thu, Jun 28, 2018 at 11:23 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> > Hi Thomas,
> >
> > In addition to above, we have xen hvm:
> >
> > setup_arch()
> > ...
> > init_hypervisor_platform();
> > x86_init.hyper.init_platform();
> > xen_hvm_guest_init()
> > xen_hvm_init_time_ops();
>
> Duh. Missed that completely.
>
> > ...
> > tsc_early_delay_calibrate();
> > tsc_khz = x86_platform.calibrate_tsc(); == xen_tsc_khz()
> > ...
> >
> > Which works early.
> >
> > So, what should we do with xen, which seems to be the only platform
> > that would provide different tsc frequency early and late, because of
> > different calibration method?
>
> Fix it? I have no idea why XEN has two variants of the scheme and I neither
> have a clue why the KVM clock stuff is late.
kvm clock I have fixed in my series.
http://lkml.kernel.org/r/20180621212518.19914-5-pasha.tatashin@oracle.com
It was late because, it depended on memblock, which is initialized later,
after e820 ranges are read.
So, after my series kvm clock will work right after
init_hypervisor_platform, the same as with most other hypervisors.
With xen, it is a little more challenging: I do not have a hardware
configured to run xen to test it.
On the other hand, most likely that tsc_early_delay_calibrate() now
fails to calibrate tsc on xen, and calibrates correctly later in
tsc_init(). I doubt, that we can use CPUID method to determine tsc
frequency on xen cpu. Anyways, that would be accidental behavior.
To make xen clock available early, we need HYPERVISOR_shared_info. So, at
least that part of xen_setup_shared_info() must be called/available from
init_hypervisor_platform():
void xen_setup_shared_info(void)
{
set_fixmap(FIX_PARAVIRT_BOOTMAP, xen_start_info->shared_info);
HYPERVISOR_shared_info =
(struct shared_info *)fix_to_virt(FIX_PARAVIRT_BOOTMAP);
xen_setup_mfn_list_list();
...
Which, I have no idea if it is possible, or safe to do.
For now, in my series, I would like check in tsc_early_init() if we are
running xen, and set tsc_khz to 0 if so. Later in tsc_init() we will get
a proper calibration. The question is how to make this check least
intrusive.
Pavel
next prev parent reply other threads:[~2018-06-29 9:00 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-21 21:25 [PATCH v12 00/11] Early boot time stamps for x86 Pavel Tatashin
2018-06-21 21:25 ` [PATCH v12 01/11] x86: text_poke() may access uninitialized struct pages Pavel Tatashin
2018-06-21 21:37 ` Randy Dunlap
2018-06-25 8:14 ` Peter Zijlstra
2018-06-25 8:39 ` Thomas Gleixner
2018-06-25 9:09 ` Peter Zijlstra
2018-06-25 9:18 ` Thomas Gleixner
2018-06-25 9:22 ` Peter Zijlstra
2018-06-25 12:32 ` Pavel Tatashin
2018-06-25 13:48 ` Peter Zijlstra
2018-06-25 14:06 ` Pavel Tatashin
2018-06-21 21:25 ` [PATCH v12 02/11] x86: initialize static branching early Pavel Tatashin
2018-06-23 9:16 ` Borislav Petkov
2018-06-23 13:11 ` Pavel Tatashin
2018-06-21 21:25 ` [PATCH v12 03/11] x86/tsc: redefine notsc to behave as tsc=unstable Pavel Tatashin
2018-06-23 13:32 ` Thomas Gleixner
2018-06-21 21:25 ` [PATCH v12 04/11] kvm/x86: remove kvm memblock dependency Pavel Tatashin
2018-06-23 13:36 ` Thomas Gleixner
2018-07-05 16:12 ` Paolo Bonzini
2018-07-06 9:24 ` Thomas Gleixner
2018-07-06 9:36 ` Paolo Bonzini
2018-07-06 9:45 ` Thomas Gleixner
2018-07-06 10:08 ` Paolo Bonzini
2018-07-06 10:44 ` Thomas Gleixner
2018-07-06 10:50 ` Thomas Gleixner
2018-07-06 15:03 ` Pavel Tatashin
2018-07-06 15:09 ` Paolo Bonzini
2018-06-21 21:25 ` [PATCH v12 05/11] s390/time: add read_persistent_wall_and_boot_offset() Pavel Tatashin
2018-06-25 7:07 ` Martin Schwidefsky
2018-06-25 12:45 ` Pavel Tatashin
2018-06-21 21:25 ` [PATCH v12 06/11] time: replace read_boot_clock64() with read_persistent_wall_and_boot_offset() Pavel Tatashin
2018-06-23 13:49 ` Thomas Gleixner
2018-06-21 21:25 ` [PATCH v12 07/11] s390/time: remove read_boot_clock64() Pavel Tatashin
2018-06-21 21:25 ` [PATCH v12 08/11] ARM/time: " Pavel Tatashin
2018-06-23 13:52 ` Thomas Gleixner
2018-06-21 21:25 ` [PATCH v12 09/11] x86/tsc: prepare for early sched_clock Pavel Tatashin
2018-06-23 16:50 ` Thomas Gleixner
2018-06-23 18:49 ` Pavel Tatashin
2018-06-23 20:11 ` Thomas Gleixner
2018-06-23 21:29 ` Pavel Tatashin
2018-06-23 23:38 ` Thomas Gleixner
2018-06-24 2:43 ` Pavel Tatashin
2018-06-24 7:30 ` Thomas Gleixner
2018-06-26 15:42 ` Thomas Gleixner
2018-06-26 18:42 ` Pavel Tatashin
2018-06-26 19:47 ` Pavel Tatashin
2018-06-28 7:31 ` Thomas Gleixner
2018-06-28 10:43 ` Thomas Gleixner
2018-06-28 11:46 ` Peter Zijlstra
2018-06-28 12:27 ` Thomas Gleixner
2018-06-28 19:42 ` Pavel Tatashin
2018-06-29 7:30 ` Thomas Gleixner
2018-06-29 8:57 ` Pavel Tatashin [this message]
2018-07-03 20:59 ` Thomas Gleixner
2018-07-02 17:18 ` Konrad Rzeszutek Wilk
2018-06-29 14:30 ` Andy Shevchenko
2018-06-29 17:50 ` Andy Shevchenko
2018-07-09 23:16 ` Boris Ostrovsky
2018-06-21 21:25 ` [PATCH v12 10/11] sched: early boot clock Pavel Tatashin
2018-06-25 8:55 ` Peter Zijlstra
2018-06-25 12:44 ` Pavel Tatashin
2018-06-25 19:23 ` Pavel Tatashin
2018-06-26 9:00 ` Peter Zijlstra
2018-06-26 11:27 ` Pavel Tatashin
2018-06-26 11:51 ` Pavel Tatashin
2018-06-26 15:07 ` Peter Zijlstra
2018-06-21 21:25 ` [PATCH v12 11/11] x86/tsc: use tsc early Pavel Tatashin
2018-06-23 16:56 ` Thomas Gleixner
2018-06-23 21:38 ` Pavel Tatashin
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