Commit 7537bae8 authored by Kuppuswamy Sathyanarayanan's avatar Kuppuswamy Sathyanarayanan Committed by Rafael J. Wysocki
Browse files

powercap: intel_rapl: Remove incorrect CPU check in PMU context 



The RAPL MSR read path incorrectly validates CPU context when called
from the PMU subsystem:

    if (atomic) {
        if (unlikely(smp_processor_id() != cpu))
            return -EIO;
        rdmsrq(ra->reg.msr, ra->value);
    }

This check fails for package-scoped MSRs like RAPL energy counters,
which are readable from any CPU within the package.

The perf tool avoids hitting this check by validating against
/sys/bus/event_source/devices/power/cpumask before opening events.
However, turbostat does not perform this validation and may attempt
reads from non-lead CPUs, causing the check to fail and return zero
power values.

Since package-scoped MSRs are architecturally accessible from any CPU
in the package, remove the CPU matching check.

Also rename 'atomic' to 'pmu_ctx' to clarify this indicates PMU context
where rdmsrq() can be used directly instead of rdmsrl_safe_on_cpu().

Fixes: 748d6ba4 ("powercap: intel_rapl: Enable MSR-based RAPL PMU support")
Signed-off-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Tested-by: default avatarFurquim Ulisses <ulisses.furquim@intel.com>
Reviewed-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20260209234310.1440722-2-sathyanarayanan.kuppuswamy@linux.intel.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 9b1b3dcd

drivers/powercap/intel_rapl_common.c

+3 −3
Original line number Diff line number Diff line
@@ -254,7 +254,7 @@ static void rapl_init_domains(struct rapl_package *rp); 
static int rapl_read_data_raw(struct rapl_domain *rd,

			      enum rapl_primitives prim,

			      bool xlate, u64 *data,

			      bool atomic);

			      bool pmu_ctx);

static int rapl_write_data_raw(struct rapl_domain *rd,

			       enum rapl_primitives prim,

			       unsigned long long value);
@@ -832,7 +832,7 @@ prim_fixups(struct rapl_domain *rd, enum rapl_primitives prim) 
 */

static int rapl_read_data_raw(struct rapl_domain *rd,

			      enum rapl_primitives prim, bool xlate, u64 *data,

			      bool atomic)

			      bool pmu_ctx)

{

	u64 value;

	enum rapl_primitives prim_fixed = prim_fixups(rd, prim);
@@ -854,7 +854,7 @@ static int rapl_read_data_raw(struct rapl_domain *rd, 


	ra.mask = rpi->mask;



	if (rd->rp->priv->read_raw(get_rid(rd->rp), &ra, atomic)) {

	if (rd->rp->priv->read_raw(get_rid(rd->rp), &ra, pmu_ctx)) {

		pr_debug("failed to read reg 0x%llx for %s:%s\n", ra.reg.val, rd->rp->name, rd->name);

		return -EIO;

	}

drivers/powercap/intel_rapl_msr.c

+5 −7
Original line number Diff line number Diff line
@@ -110,16 +110,14 @@ static int rapl_cpu_down_prep(unsigned int cpu) 
	return 0;

}



static int rapl_msr_read_raw(int cpu, struct reg_action *ra, bool atomic)

static int rapl_msr_read_raw(int cpu, struct reg_action *ra, bool pmu_ctx)

{

	/*

	 * When called from atomic-context (eg PMU event handler)

	 * perform MSR read directly using rdmsrq().

	 * When called from PMU context, perform MSR read directly using

	 * rdmsrq() without IPI overhead. Package-scoped MSRs are readable

	 * from any CPU in the package.

	 */

	if (atomic) {

		if (unlikely(smp_processor_id() != cpu))

			return -EIO;



	if (pmu_ctx) {

		rdmsrq(ra->reg.msr, ra->value);

		goto out;

	}

include/linux/intel_rapl.h

+1 −1
Original line number Diff line number Diff line
@@ -152,7 +152,7 @@ struct rapl_if_priv { 
	union rapl_reg reg_unit;

	union rapl_reg regs[RAPL_DOMAIN_MAX][RAPL_DOMAIN_REG_MAX];

	int limits[RAPL_DOMAIN_MAX];

	int (*read_raw)(int id, struct reg_action *ra, bool atomic);

	int (*read_raw)(int id, struct reg_action *ra, bool pmu_ctx);

	int (*write_raw)(int id, struct reg_action *ra);

	void *defaults;

	void *rpi;