linux-kernel - Re: [Xen-devel] HPET enabled in BIOS, not presented as available_clocksource -- config, kernel code, &/or BIOS?

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Date:   Sun, 14 May 2017 10:41:17 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Andrew Cooper <andrew.cooper3@...rix.com>, pgnet.dev@...il.com,
        Valentin Vidic <Valentin.Vidic@...Net.hr>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Clemens Ladisch <clemens@...isch.de>,
        xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] HPET enabled in BIOS, not presented as
 available_clocksource -- config, kernel code, &/or BIOS?

On 05/14/17 08:39, Andrew Cooper wrote:
> On 14/05/17 00:17, PGNet Dev wrote:
>> On 5/13/17 3:15 PM, Valentin Vidic wrote:
>>> Try booting without 'hpet=force,verbose clocksource=hpet' and it should
>>> select xen by default:
>> Nope. Well, not quite ...
>>
>> With both 
>>
>> 	'hpet=force,verbose clocksource=hpet'
>>
>> removed, I end up with
>>
>> 	cat /sys/devices/system/clocksource/clocksource0/available_clocksource
>> 		tsc xen
>> 	cat /sys/devices/system/clocksource/clocksource0/current_clocksource
>> 		tsc
>>
>> But with 
>>
>> 	clocksource=xen
>>
>> *explicitly* added
>>
>> 	cat /sys/devices/system/clocksource/clocksource0/available_clocksource
>> 		tsc xen
>> 	cat /sys/devices/system/clocksource/clocksource0/current_clocksourcexen
>> 		xen
>>
>> and in *console*, NOT dmesg, output,
>>
>> 	grep -i hpet tmp.txt
>> 		(XEN) ACPI: HPET 9E8298F8, 0038 (r1 SUPERM SMCI--MB  1072009 AMI.        5)
>> 		(XEN) ACPI: HPET id: 0x8086a701 base: 0xfed00000
>> 		(XEN) [VT-D] MSI HPET: 0000:f0:0f.0
>> 		(XEN) Platform timer is 14.318MHz HPET
>> 		[    0.000000] ACPI: HPET 0x000000009E8298F8 000038 (v01 SUPERM SMCI--MB 01072009 AMI. 000000
>> 		[    0.000000] ACPI: HPET id: 0x8086a701 base: 0xfed00000
>> 		[    0.000000] ACPI: HPET 0x000000009E8298F8 000038 (v01 SUPERM SMCI--MB 01072009 AMI. 000000
>> 		[    0.000000] ACPI: HPET id: 0x8086a701 base: 0xfed00000
>> 		[    8.515245] hpet_acpi_add: no address or irqs in _CRS
>> 		[    8.515245] hpet_acpi_add: no address or irqs in _CRS
>> 		(XEN) [2017-05-13 23:04:27] HVM1 save: HPET
>>
>>
>>
>> and
>>
>> 	dmesg | grep -i clocksource | grep -v line:
>> 		[    0.000000] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645519600211568 ns
>> 		[    0.004000] clocksource: xen: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
>> 		[    0.375709] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
>> 		[    4.656634] clocksource: Switched to clocksource xen
>> 		[    8.912897] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x2c94dffea94, max_idle_ns: 440795361700 ns
>>
>> jiffies, now? hm. no idea where that came from. and why the 'tsc' ?
>>
>> So I'm still unclear -- is this^ now, correctly "all" using MSI/HPET?
> 
> What are you trying to achieve?  It is still not clear despite all on
> this thread.

I agree.  Are you (pgnet.dev) just curious about why the Xen kernel does
not expose HPET as a clocksource or is not having it causing some problem
for you or some specific software application?


> The Linux HEPT error messages are non-ideal, but there is no way dom0
> will ever be able to use clocksource=hpet when running under Xen.



-- 
~Randy