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.pandruv...@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?
> + 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().
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
