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Date: Fri, 18 Nov 2022 18:57:24 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: rafael@...nel.org, daniel.lezcano@...aro.org, amitk@...nel.org,
rui.zhang@...el.com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH RESEND 2/2] thermal: intel: Protect clearing of thermal
status bits
On Wed, Nov 16, 2022 at 3:54 AM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> The clearing of the package thermal status is done by Read-Modify-Write
> operation. This may result in clearing of some new status bits which are
> being or about to be processed.
>
> For example, while clearing of HFI status, after read of thermal status
> register, a new thermal status bit is set by the hardware. But during
> write back, the newly generated status bit will be set to 0 or cleared.
> So, it is not safe to do read-modify-write.
>
> Since thermal status Read-Write bits can be set to only 0 not 1, it is
> safe to set all other bits to 1 which are not getting cleared.
>
> Create a common interface for clearing package thermal status bits. Use
> this interface to replace existing code to clear thermal package status
> bits.
>
> It is safe to call from different CPUs without protection as there is no
> read-modify-write. Also wrmsrl results in just single instruction. For
> example while CPU 0 and CPU 3 are clearing bit 1 and 3 respectively. If
> CPU 3 wins the race, it will write 0x4000aa2, then CPU 1 will write
> 0x4000aa8. The bits which are not part of clear are set to 1. The default
> mask for bits, which can be written here is 0x4000aaa.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
How urgent is this? Would 6.2 be sufficient?
Also, do you want it to go into -stable?
> ---
> Email address was wrong, so sending again.
>
> drivers/thermal/intel/intel_hfi.c | 8 ++-----
> drivers/thermal/intel/therm_throt.c | 23 ++++++++++----------
> drivers/thermal/intel/thermal_interrupt.h | 6 +++++
> drivers/thermal/intel/x86_pkg_temp_thermal.c | 9 ++------
> 4 files changed, 22 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
> index a0640f762dc5..c9e0827c9ebe 100644
> --- a/drivers/thermal/intel/intel_hfi.c
> +++ b/drivers/thermal/intel/intel_hfi.c
> @@ -42,9 +42,7 @@
>
> #include "../thermal_core.h"
> #include "intel_hfi.h"
> -
> -#define THERM_STATUS_CLEAR_PKG_MASK (BIT(1) | BIT(3) | BIT(5) | BIT(7) | \
> - BIT(9) | BIT(11) | BIT(26))
> +#include "thermal_interrupt.h"
>
> /* Hardware Feedback Interface MSR configuration bits */
> #define HW_FEEDBACK_PTR_VALID_BIT BIT(0)
> @@ -304,9 +302,7 @@ void intel_hfi_process_event(__u64 pkg_therm_status_msr_val)
> * Let hardware know that we are done reading the HFI table and it is
> * free to update it again.
> */
> - pkg_therm_status_msr_val &= THERM_STATUS_CLEAR_PKG_MASK &
> - ~PACKAGE_THERM_STATUS_HFI_UPDATED;
> - wrmsrl(MSR_IA32_PACKAGE_THERM_STATUS, pkg_therm_status_msr_val);
> + thermal_clear_package_intr_status(PACKAGE_LEVEL, PACKAGE_THERM_STATUS_HFI_UPDATED);
>
> queue_delayed_work(hfi_updates_wq, &hfi_instance->update_work,
> HFI_UPDATE_INTERVAL);
> diff --git a/drivers/thermal/intel/therm_throt.c b/drivers/thermal/intel/therm_throt.c
> index 9e8ab31d756e..4bb7fddaa143 100644
> --- a/drivers/thermal/intel/therm_throt.c
> +++ b/drivers/thermal/intel/therm_throt.c
> @@ -190,32 +190,33 @@ static const struct attribute_group thermal_attr_group = {
> };
> #endif /* CONFIG_SYSFS */
>
> -#define CORE_LEVEL 0
> -#define PACKAGE_LEVEL 1
> -
> #define THERM_THROT_POLL_INTERVAL HZ
> #define THERM_STATUS_PROCHOT_LOG BIT(1)
>
> #define THERM_STATUS_CLEAR_CORE_MASK (BIT(1) | BIT(3) | BIT(5) | BIT(7) | BIT(9) | BIT(11) | BIT(13) | BIT(15))
> #define THERM_STATUS_CLEAR_PKG_MASK (BIT(1) | BIT(3) | BIT(5) | BIT(7) | BIT(9) | BIT(11) | BIT(26))
>
> -static void clear_therm_status_log(int level)
> +/*
> + * Clear the bits in package thermal status register for bit = 1
> + * in bitmask
> + */
> +void thermal_clear_package_intr_status(int level, u64 bit_mask)
> {
> + u64 msr_val;
> int msr;
> - u64 mask, msr_val;
>
> if (level == CORE_LEVEL) {
> msr = MSR_IA32_THERM_STATUS;
> - mask = THERM_STATUS_CLEAR_CORE_MASK;
> + msr_val = THERM_STATUS_CLEAR_CORE_MASK;
> } else {
> msr = MSR_IA32_PACKAGE_THERM_STATUS;
> - mask = THERM_STATUS_CLEAR_PKG_MASK;
> + msr_val = THERM_STATUS_CLEAR_PKG_MASK;
> }
>
> - rdmsrl(msr, msr_val);
> - msr_val &= mask;
> - wrmsrl(msr, msr_val & ~THERM_STATUS_PROCHOT_LOG);
> + msr_val &= ~bit_mask;
> + wrmsrl(msr, msr_val);
> }
> +EXPORT_SYMBOL_GPL(thermal_clear_package_intr_status);
>
> static void get_therm_status(int level, bool *proc_hot, u8 *temp)
> {
> @@ -295,7 +296,7 @@ static void __maybe_unused throttle_active_work(struct work_struct *work)
> state->average = avg;
>
> re_arm:
> - clear_therm_status_log(state->level);
> + thermal_clear_package_intr_status(state->level, THERM_STATUS_PROCHOT_LOG);
> schedule_delayed_work_on(this_cpu, &state->therm_work, THERM_THROT_POLL_INTERVAL);
> }
>
> diff --git a/drivers/thermal/intel/thermal_interrupt.h b/drivers/thermal/intel/thermal_interrupt.h
> index 01e7bed2ffc7..01dfd4cdb5df 100644
> --- a/drivers/thermal/intel/thermal_interrupt.h
> +++ b/drivers/thermal/intel/thermal_interrupt.h
> @@ -2,6 +2,9 @@
> #ifndef _INTEL_THERMAL_INTERRUPT_H
> #define _INTEL_THERMAL_INTERRUPT_H
>
> +#define CORE_LEVEL 0
> +#define PACKAGE_LEVEL 1
> +
> /* Interrupt Handler for package thermal thresholds */
> extern int (*platform_thermal_package_notify)(__u64 msr_val);
>
> @@ -15,4 +18,7 @@ extern bool (*platform_thermal_package_rate_control)(void);
> /* Handle HWP interrupt */
> extern void notify_hwp_interrupt(void);
>
> +/* Common function to clear Package thermal status register */
> +extern void thermal_clear_package_intr_status(int level, u64 bit_mask);
> +
> #endif /* _INTEL_THERMAL_INTERRUPT_H */
> diff --git a/drivers/thermal/intel/x86_pkg_temp_thermal.c b/drivers/thermal/intel/x86_pkg_temp_thermal.c
> index a0e234fce71a..84c3a116ed04 100644
> --- a/drivers/thermal/intel/x86_pkg_temp_thermal.c
> +++ b/drivers/thermal/intel/x86_pkg_temp_thermal.c
> @@ -265,7 +265,6 @@ static void pkg_temp_thermal_threshold_work_fn(struct work_struct *work)
> struct thermal_zone_device *tzone = NULL;
> int cpu = smp_processor_id();
> struct zone_device *zonedev;
> - u64 msr_val, wr_val;
>
> mutex_lock(&thermal_zone_mutex);
> raw_spin_lock_irq(&pkg_temp_lock);
> @@ -279,12 +278,8 @@ static void pkg_temp_thermal_threshold_work_fn(struct work_struct *work)
> }
> zonedev->work_scheduled = false;
>
> - rdmsrl(MSR_IA32_PACKAGE_THERM_STATUS, msr_val);
> - wr_val = msr_val & ~(THERM_LOG_THRESHOLD0 | THERM_LOG_THRESHOLD1);
> - if (wr_val != msr_val) {
> - wrmsrl(MSR_IA32_PACKAGE_THERM_STATUS, wr_val);
> - tzone = zonedev->tzone;
> - }
> + thermal_clear_package_intr_status(PACKAGE_LEVEL, THERM_LOG_THRESHOLD0 | THERM_LOG_THRESHOLD1);
> + tzone = zonedev->tzone;
>
> enable_pkg_thres_interrupt();
> raw_spin_unlock_irq(&pkg_temp_lock);
> --
> 2.31.1
>
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