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powercap: intel_rapl: Remove incorrect CPU check in PMU context

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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: 748d6ba43a ("powercap: intel_rapl: Enable MSR-based RAPL PMU support")
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Tested-by: Furquim Ulisses <ulisses.furquim@intel.com>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://patch.msgid.link/20260209234310.1440722-2-sathyanarayanan.kuppuswamy@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Kuppuswamy Sathyanarayanan 2026-02-09 15:43:09 -08:00 • committed by Rafael J. Wysocki
parent 9b1b3dcd28
commit 7537bae8b6
3 changed files with 9 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

6
drivers/powercap/intel_rapl_common.c
View file

@ -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;
}

12
drivers/powercap/intel_rapl_msr.c
View file

@ -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;
}

2
include/linux/intel_rapl.h
View file

@ -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;