From: Dou Liyang <douly.fnst@cn.fujitsu.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@redhat.com>,
Mathias Nyman <mathias.nyman@linux.intel.com>,
<tglx@linutronix.de>
Cc: <peterz@infradead.org>, <linux-usb@vger.kernel.org>,
<x86@kernel.org>, <linux-kernel@vger.kernel.org>,
Juergen Gross <jgross@suse.com>,
xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v8 1/5] x86: add simple udelay calibration
Date: Thu, 13 Jul 2017 09:39:38 +0800 [thread overview]
Message-ID: <4b423b45-3b83-ead5-1205-a004d13dac77@cn.fujitsu.com> (raw)
In-Reply-To: <5966CA3F.2030402@linux.intel.com>
Hi, Lu
At 07/13/2017 09:17 AM, Lu Baolu wrote:
> Hi,
>
> On 07/12/2017 04:02 PM, Dou Liyang wrote:
>> Hi, Lu
>>
>> At 05/05/2017 08:50 PM, Boris Ostrovsky wrote:
>>> On 05/05/2017 01:41 AM, Lu Baolu wrote:
>>>> Hi,
>>>>
>>>> On 05/03/2017 06:38 AM, Boris Ostrovsky wrote:
>>>>> On 03/21/2017 04:01 AM, Lu Baolu wrote:
>>>>>> Add a simple udelay calibration in x86 architecture-specific
>>>>>> boot-time initializations. This will get a workable estimate
>>>>>> for loops_per_jiffy. Hence, udelay() could be used after this
>>>>>> initialization.
>>>>> This breaks Xen PV guests since at this point, and until
>>>>> x86_init.paging.pagetable_init() which is when pvclock_vcpu_time_info is
>>>>> mapped, they cannot access pvclock.
>>>>>
>>>>> Is it reasonable to do this before tsc_init() is called? (The failure
>>>>> has nothing to do with tsc_init(), really --- it's just that it is
>>>>> called late enough that Xen PV guests get properly initialized.) If it
>>>>> is, would it be possible to move simple_udelay_calibration() after
>>>>> x86_init.paging.pagetable_init()?
>>>> This is currently only used for bare metal. How about by-pass it
>>>> for Xen PV guests?
>>>
>>> It is fixed this for Xen PV guests now (in the sense that we don't crash
>>> anymore) but my question is still whether this is not too early. Besides
>>> tsc_init() (which might not be important here), at the time when
>>> simple_udelay_calibration() is invoked we haven't yet called:
>>> * kvmclock_init(), which sets calibration routines for KVM
>>> * init_hypervisor_platform(), which sets calibration routines for vmware
>>> and Xen HVM
>>> * x86_init.paging.pagetable_init(), which sets calibration routines for
>>> Xen PV
>>>
>>
>> I guess these may have been missed.
>>
>> Do you have any comments about these?
>>
>
> The patch will be available in 4.13-rc1.
Yes, I have seen it in the upstream.
Firstly, I also met this problem want to call udelay() earlier than
*loops_per_jiffy* setup like you[1]. So I am very interesting in this
patch. ;)
I am also confused about the questions which Boris asked:
whether do the CPU and TSC calibration too early just for using
udelay()?
this design broke our interface of x86_paltform.calibrate_cpu/tsc.
And I also have a question below.
[...]
>>>>>>
>>>>>> +static void __init simple_udelay_calibration(void)
>>>>>> +{
>>>>>> + unsigned int tsc_khz, cpu_khz;
>>>>>> + unsigned long lpj;
>>>>>> +
>>>>>> + if (!boot_cpu_has(X86_FEATURE_TSC))
>>>>>> + return;
if we don't have the TSC feature in booting CPU and
it returns here, can we use udelay() correctly like before?
[1] https://lkml.org/lkml/2017/7/3/276
Thanks,
dou.
>> Thanks,
>>
>> dou.
>>
>>>>>> +
>>>>>> + cpu_khz = x86_platform.calibrate_cpu();
>>>>>> + tsc_khz = x86_platform.calibrate_tsc();
>>>>>> +
>>>>>> + tsc_khz = tsc_khz ? : cpu_khz;
>>>>>> + if (!tsc_khz)
>>>>>> + return;
>>>>>> +
>>>>>> + lpj = tsc_khz * 1000;
>>>>>> + do_div(lpj, HZ);
>>>>>> + loops_per_jiffy = lpj;
>>>>>> +}
>>>>>> +
>>>>>> /*
>>>>>> * Determine if we were loaded by an EFI loader. If so, then we have also been
>>>>>> * passed the efi memmap, systab, etc., so we should use these data structures
>>>>>> @@ -985,6 +1005,8 @@ void __init setup_arch(char **cmdline_p)
>>>>>> */
>>>>>> x86_configure_nx();
>>>>>>
>>>>>> + simple_udelay_calibration();
>>>>>> +
>>>>>> parse_early_param();
>>>>>>
>>>>>> #ifdef CONFIG_MEMORY_HOTPLUG
>>>
>>>
>>>
>>>
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-usb" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
>
>
>
next prev parent reply other threads:[~2017-07-13 1:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-21 8:01 [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Lu Baolu
2017-03-21 8:01 ` [PATCH v8 1/5] x86: add simple udelay calibration Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] x86/timers: Add " tip-bot for Lu Baolu
2017-05-24 16:56 ` Jan Kiszka
2017-05-25 0:49 ` Lu Baolu
2017-05-02 22:38 ` [PATCH v8 1/5] x86: add " Boris Ostrovsky
2017-05-05 5:41 ` Lu Baolu
2017-05-05 12:50 ` Boris Ostrovsky
2017-07-12 8:02 ` Dou Liyang
2017-07-13 1:17 ` Lu Baolu
2017-07-13 1:39 ` Dou Liyang [this message]
2017-07-13 3:00 ` Lu Baolu
2017-07-14 3:21 ` Dou Liyang
2017-03-21 8:01 ` [PATCH v8 2/5] usb: early: add driver for xhci debug capability Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] usb/early: Add " tip-bot for Lu Baolu
2017-05-30 13:46 ` [PATCH v8 2/5] usb: early: add " Vlastimil Babka
2017-05-31 3:27 ` Lu Baolu
2017-05-31 6:24 ` Steven Rostedt
2017-06-01 3:35 ` Lu Baolu
2017-05-31 9:38 ` Vlastimil Babka
2017-06-01 3:37 ` Lu Baolu
2017-06-01 8:15 ` Vlastimil Babka
2017-06-01 12:25 ` Peter Zijlstra
2017-06-02 0:47 ` Steven Rostedt
2017-03-21 8:01 ` [PATCH v8 3/5] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2017-03-21 12:20 ` [tip:x86/debug] x86/earlyprintk: Add " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 4/5] usb: serial: add dbc debug device support to usb_debug Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/serial: Add DBC " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/doc: Add " tip-bot for Lu Baolu
2017-03-21 11:33 ` [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Ingo Molnar
2017-03-21 12:27 ` Greg Kroah-Hartman
2017-03-21 12:46 ` Ingo Molnar
2017-03-22 2:23 ` Lu Baolu
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