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

[Vitaly Kuznetsov]

Andrei Borzenkov <address@hidden> writes:

> 01.12.2015 11:34, Vitaly Kuznetsov пишет:
>> 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.
>> 
>
> Thank you! I pushed fix, if you could verify that master now works on
> Hyper-V would be great.

Just tested grub-2.02-beta2-562-ga03c103, works as well. Thanks!

-- 
  Vitaly