Andrei Borzenkov <arvidj...@gmail.com> writes:
> 30.11.2015 19:50, Andrei Borzenkov пишет:
>> 30.11.2015 19:31, Vitaly Kuznetsov пишет:
>>> Andrei Borzenkov <arvidj...@gmail.com> 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?
>>
>
> 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
I've instrumented pit_calibrate_tsc() in Linux and can confirm inb(0x61)
returns 0xff on Hyper-V Gen2 VMs.
> so this will always
> succeed, right? Linux kernel is using some sanity checks, if loop
> terminated too early it assumes calibration failure.
--
Vitaly
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