Re: [PATCH v3] acpi: Issue _OSC call for native thermal interrupt handling

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Thu, 2016-03-17 at 10:36 +0100, Borislav Petkov wrote:
> On Wed, Mar 16, 2016 at 07:05:37PM -0700, Srinivas Pandruvada wrote:
> > There are several reports of freeze on enabling HWP (Hardware
> > PStates)
> > feature on Skylake based systems by Intel P states driver. The root
> > cause is identified as the HWP interrupts causing BIOS code to
> > freeze.
> > HWP interrupts uses thermal LVT.
> > Linux natively handles thermal interrupts, but in Skylake based
> > systems
> > SMM will take control of thermal interrupts. This is a problem for
> > several
> > reasons:
> > - It is freezing in BIOS when tries to handle thermal interrupt,
> > which
> > will require BIOS upgrade
> > - With SMM handling thermal we loose all the reporting features of
> > Linux arch/x86/kernel/cpu/mcheck/therm_throt driver
> > - Some thermal drivers like x86-package-temp driver depends on the
> > thermal
> > threshold interrupts
> > - The HWP interrupts are useful for debugging and tuning
> > performance
> > 
> > So we need native handling of thermal interrupts. To inform SMM
> > that
> > OS will handle thermal interrupts, we need to use _OSC under
> > processor
> > scope very early in ACPI initialization flow. This needs to be done
> > before SMM code path looks for _OSC capabilities. The bit 12 of
> > _OSC in processor scope defines whether OS will handle thermal
> > interrupts.
> > When bit 12 is set to 1, OS will handle thermal interrupts.
> > Refer to this document for details on _OSC
> > http://www.intel.com/content/www/us/en/standards/processor-vendor-
> > specific-acpi-specification.html
> > 
> > This change introduces a new function
> > acpi_early_processor_set_osc(),
> > which walks acpi name space and finds acpi processor object and
> > set capability via _OSC method to take over thermal LVT.
> > 
> > Also this change writes HWP status bits to 0 to clear any HWP
> > status
> > bits in intel_thermal_interrupt().
> > 
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel
> > .com>
> > ---
> > v3:
> > - Added CONFIG_X86 around static_cpu_has() to fix compile error on
> > ARCH=ia64, reported by kbuild test robot
> > - return AE_CTRL_TERMINATE to terminate acpi name walk space, when
> > _OSC
> > is set already once.
> > v2:
> > Unnecessary newline was introduced, removed that in
> > acpi_processor.c
> > 
> >  arch/x86/kernel/cpu/mcheck/therm_throt.c |  8 ++++++
> >  drivers/acpi/acpi_processor.c            | 47
> > ++++++++++++++++++++++++++++++++
> >  drivers/acpi/bus.c                       |  3 ++
> >  drivers/acpi/internal.h                  |  2 ++
> >  4 files changed, 60 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > b/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > index 2c5aaf8..4599012 100644
> > --- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > +++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
> > @@ -79,6 +79,8 @@ static atomic_t therm_throt_en	=
> > ATOMIC_INIT(0);
> >  
> >  static u32 lvtthmr_init __read_mostly;
> >  
> > +static bool thermal_hwp_interrupt_support;
> > +
> >  #ifdef CONFIG_SYSFS
> >  #define define_therm_throt_device_one_ro(_name)			
> > 	\
> >  	static DEVICE_ATTR(_name, 0444,				
> > 	\
> > @@ -385,6 +387,9 @@ static void intel_thermal_interrupt(void)
> >  {
> >  	__u64 msr_val;
> >  
> > +	if (thermal_hwp_interrupt_support)
> 
> Why the intermittent variable and not using static_cpu_has()
> directly?
If that's what you prefer, I will do that.

> > +		wrmsrl_safe(MSR_HWP_STATUS, 0);
> > +
> >  	rdmsrl(MSR_IA32_THERM_STATUS, msr_val);
> >  
> >  	/* Check for violation of core thermal thresholds*/
> > @@ -553,6 +558,9 @@ void intel_init_thermal(struct cpuinfo_x86 *c)
> >  	rdmsr(MSR_IA32_MISC_ENABLE, l, h);
> >  	wrmsr(MSR_IA32_MISC_ENABLE, l | MSR_IA32_MISC_ENABLE_TM1,
> > h);
> >  
> > +	if (static_cpu_has(X86_FEATURE_HWP))
> > +		thermal_hwp_interrupt_support = true;
> > +
> >  	/* Unmask the thermal vector: */
> >  	l = apic_read(APIC_LVTTHMR);
> >  	apic_write(APIC_LVTTHMR, l & ~APIC_LVT_MASKED);
> > diff --git a/drivers/acpi/acpi_processor.c
> > b/drivers/acpi/acpi_processor.c
> > index 6979186..55ad24d 100644
> > --- a/drivers/acpi/acpi_processor.c
> > +++ b/drivers/acpi/acpi_processor.c
> > @@ -491,6 +491,53 @@ static void acpi_processor_remove(struct
> > acpi_device *device)
> >  }
> >  #endif /* CONFIG_ACPI_HOTPLUG_CPU */
> >  
> > +#ifdef CONFIG_X86
> > +static bool acpi_hwp_native_thermal_lvt_set;
> > +static acpi_status acpi_set_hwp_native_thermal_lvt_osc(acpi_handle
> > handle,
> > +						       u32 lvl,
> > void *context,
> > +						       void **rv)
> > +{
> > +	u8 sb_uuid_str[] = "4077A616-290C-47BE-9EBD-D87058713953";
> > +	u32 capbuf[2];
> > +	struct acpi_osc_context osc_context = {
> > +		.uuid_str = sb_uuid_str,
> > +		.rev = 1,
> > +		.cap.length = 8,
> > +		.cap.pointer = capbuf,
> > +	};
> > +
> > +	if (acpi_hwp_native_thermal_lvt_set)
> > +		return AE_CTRL_TERMINATE;
> > +
> > +	capbuf[0] = 0x0000;
> > +	capbuf[1] = 0x1000; /* set bit 12 */
> > +
> > +	if (ACPI_SUCCESS(acpi_run_osc(handle, &osc_context))) {
> > +		acpi_hwp_native_thermal_lvt_set = true;
> > +		kfree(osc_context.ret.pointer);
> > +	}
> > +
> > +	return AE_OK;
> > +}
> > +
> > +void acpi_early_processor_set_osc(void)
> > +{
> > +	if (static_cpu_has(X86_FEATURE_HWP)) {
> 
> This one can be boot_cpu_has().
I will give a try.

Thanks,
Srinivas