Re: [PATCH] calibrate_tsc(): use the Stall() EFI boot service on GRUB_MACHINE_EFI

[Vitaly Kuznetsov]

Michael Chang <address@hidden> writes:

> On Mon, Nov 30, 2015 at 08:34:18PM +0300, Andrei Borzenkov wrote:
>> 30.11.2015 19:50, Andrei Borzenkov пишет:
>> > 30.11.2015 19:31, Vitaly Kuznetsov пишет:
>> >> Andrei Borzenkov <address@hidden> writes:
>> >>
>> >>> 26.11.2014 11:59, Laszlo Ersek пишет:
>> >>>> HyperV Gen2 virtual machines have no PIT; guest code should rely on UEFI
>> >>>> services instead.
>> >>>>
>> >>>
>> >>> Could you retest with current master? It now supports multiple methods
>> >>> to calibrate TSC and should avoid PIT on UEFI systems.
>> >>
>> >> Unfortunately, current master (grub-2.02-beta2-561-g346a494) still
>> >> doesn't work for me, timer keeps running like crazy on Gen2 Hyper-V VMs.
>> >>
>> > 
>> > @Michael: I remember you tested version of Vladimir patch on Hyper-V?
>> > Could you test current master?
>> > 
>
> I don't have access to Hyper-V either. My initial patch was tested on
> Hyper-V from my colleage in Nuremburg. For Vladimir's patch I did tests
> on my EFI machine and mostly intersted in pmtimer to function properly,
> as that's new introduced timer to the patch .. 
>
>> 
>> 
>>   if ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH)) {
>>     ret = 1;
>>     /* Wait.  */
>>     while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH)
>> == 0x00);
>>   }
>> 
>> 
>> If PIT is not present all reads should return 0xff so this will always
>> succeed, right? Linux kernel is using some sanity checks, if loop
>> terminated too early it assumes calibration failure.
>
> Well, yes the detection is bogus, I think the condition should check for
> return 0x00, which means the timer is counting and can continue to wait
> for it to finish.
>
>    if ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0) {
>      ret = 1;
>      /* Wait.  */
>      while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH)
>  == 0x00);
>    }
>
> Vitaly, could you please help to retest ?
>

Sure,

just did and with this change timer seems to be working as expected.

-- 
  Vitaly