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?
Best regards,
Lu Baolu
>
> -boris
>
>
>> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>> Cc: x86@xxxxxxxxxx
>> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
>> ---
>> arch/x86/kernel/setup.c | 22 ++++++++++++++++++++++
>> 1 file changed, 22 insertions(+)
>>
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 4bf0c89..e70204e 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -837,6 +837,26 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
>> return 0;
>> }
>>
>> +static void __init simple_udelay_calibration(void)
>> +{
>> + unsigned int tsc_khz, cpu_khz;
>> + unsigned long lpj;
>> +
>> + if (!boot_cpu_has(X86_FEATURE_TSC))
>> + return;
>> +
>> + 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
>
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