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Thu, 24 Jul 2025 14:22:36 -0700 (PDT) Received: from dev-machine ([2607:fb90:33af:1e63:f0a9:3023:5b5f:ebde]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23fa476ea14sm22496555ad.58.2025.07.24.14.22.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Jul 2025 14:22:36 -0700 (PDT) From: Niko Nikolov To: ray.huang@amd.com, gautham.shenoy@amd.com, mario.limonciello@amd.com Cc: perry.yuan@amd.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, shuah@kernel.org, Niko Nikolov Subject: [PATCH] x86/amd/power: Replace do_div() with div64_u64() Date: Thu, 24 Jul 2025 14:21:05 -0700 Message-ID: <20250724212221.9964-1-nikolay.niko.nikolov@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" do_div() divides 64-by-32, and can risk truncation if divisor exceeds 32 bi= ts. Use div64_u64() for full 64/64-bit division as recommended, resolving stati= c analysis warnings. Signed-off-by: Niko Nikolov --- arch/x86/events/amd/power.c | 49 ++++++++++++++++++------------------- 1 file changed, 24 insertions(+), 25 deletions(-) diff --git a/arch/x86/events/amd/power.c b/arch/x86/events/amd/power.c index dad42790cf7d..35eff3383660 100644 --- a/arch/x86/events/amd/power.c +++ b/arch/x86/events/amd/power.c @@ -15,12 +15,12 @@ #include "../perf_event.h" =20 /* Event code: LSB 8 bits, passed in attr->config any other bit is reserve= d. */ -#define AMD_POWER_EVENT_MASK 0xFFULL +#define AMD_POWER_EVENT_MASK 0xFFULL =20 /* * Accumulated power status counters. */ -#define AMD_POWER_EVENTSEL_PKG 1 +#define AMD_POWER_EVENTSEL_PKG 1 =20 /* * The ratio of compute unit power accumulator sample period to the @@ -65,7 +65,7 @@ static void event_update(struct perf_event *event) delta *=3D cpu_pwr_sample_ratio * 1000; tdelta =3D new_ptsc - prev_ptsc; =20 - do_div(delta, tdelta); + div64_u64(delta, tdelta); local64_add(delta, &event->count); } =20 @@ -144,8 +144,8 @@ static void pmu_event_read(struct perf_event *event) event_update(event); } =20 -static ssize_t -get_attr_cpumask(struct device *dev, struct device_attribute *attr, char *= buf) +static ssize_t get_attr_cpumask(struct device *dev, + struct device_attribute *attr, char *buf) { return cpumap_print_to_pagebuf(true, buf, &cpu_mask); } @@ -165,12 +165,12 @@ static struct attribute_group pmu_attr_group =3D { * Currently it only supports to report the power of each * processor/package. */ -EVENT_ATTR_STR(power-pkg, power_pkg, "event=3D0x01"); +EVENT_ATTR_STR(power - pkg, power_pkg, "event=3D0x01"); =20 -EVENT_ATTR_STR(power-pkg.unit, power_pkg_unit, "mWatts"); +EVENT_ATTR_STR(power - pkg.unit, power_pkg_unit, "mWatts"); =20 /* Convert the count from micro-Watts to milli-Watts. */ -EVENT_ATTR_STR(power-pkg.scale, power_pkg_scale, "1.000000e-3"); +EVENT_ATTR_STR(power - pkg.scale, power_pkg_scale, "1.000000e-3"); =20 static struct attribute *events_attr[] =3D { EVENT_PTR(power_pkg), @@ -180,8 +180,8 @@ static struct attribute *events_attr[] =3D { }; =20 static struct attribute_group pmu_events_group =3D { - .name =3D "events", - .attrs =3D events_attr, + .name =3D "events", + .attrs =3D events_attr, }; =20 PMU_FORMAT_ATTR(event, "config:0-7"); @@ -192,8 +192,8 @@ static struct attribute *formats_attr[] =3D { }; =20 static struct attribute_group pmu_format_group =3D { - .name =3D "format", - .attrs =3D formats_attr, + .name =3D "format", + .attrs =3D formats_attr, }; =20 static const struct attribute_group *attr_groups[] =3D { @@ -204,17 +204,17 @@ static const struct attribute_group *attr_groups[] = =3D { }; =20 static struct pmu pmu_class =3D { - .attr_groups =3D attr_groups, + .attr_groups =3D attr_groups, /* system-wide only */ - .task_ctx_nr =3D perf_invalid_context, - .event_init =3D pmu_event_init, - .add =3D pmu_event_add, - .del =3D pmu_event_del, - .start =3D pmu_event_start, - .stop =3D pmu_event_stop, - .read =3D pmu_event_read, - .capabilities =3D PERF_PMU_CAP_NO_EXCLUDE, - .module =3D THIS_MODULE, + .task_ctx_nr =3D perf_invalid_context, + .event_init =3D pmu_event_init, + .add =3D pmu_event_add, + .del =3D pmu_event_del, + .start =3D pmu_event_start, + .stop =3D pmu_event_stop, + .read =3D pmu_event_read, + .capabilities =3D PERF_PMU_CAP_NO_EXCLUDE, + .module =3D THIS_MODULE, }; =20 static int power_cpu_exit(unsigned int cpu) @@ -278,10 +278,9 @@ static int __init amd_power_pmu_init(void) return -ENODEV; } =20 - cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_POWER_ONLINE, - "perf/x86/amd/power:online", - power_cpu_init, power_cpu_exit); + "perf/x86/amd/power:online", power_cpu_init, + power_cpu_exit); =20 ret =3D perf_pmu_register(&pmu_class, "power", -1); if (WARN_ON(ret)) { --=20 2.50.1 Hi, This patch replaces do_div() with div64_u64() in arch/x86/events/amd/power.c to avoid potential truncation/overflow, and to conform to kernel arithmetic best practices. It builds cleanly for me, but I do not have AMD hardware available to test functionality at runtime, so additional testing on AMD systems would be appreciated. Thanks, Niko Nikolov