perf/amd/ibs: Add ->check_period() callback

IBS Fetch and IBS Op PMUs have constraints on sample period. The sample
period is verified at the time of opening an event but not at the ioctl()
interface. Hence, a user can open an event with valid period but change
it later with ioctl(). Add a ->check_period() callback to verify the
period provided at ioctl() is also valid.

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/r/20250115054438.1021-8-ravi.bangoria@amd.com

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 7b54b76d39f5d83058d499dec2625b50603dcc3c..aea893a971b6e2d231fcf9618ea1699f7740f93d 100644 (file)
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -564,6 +564,28 @@ static void perf_ibs_del(struct perf_event *event, int flags)
 
 static void perf_ibs_read(struct perf_event *event) { }
 
+static int perf_ibs_check_period(struct perf_event *event, u64 value)
+{
+       struct perf_ibs *perf_ibs;
+       u64 low_nibble;
+
+       if (event->attr.freq)
+               return 0;
+
+       perf_ibs = container_of(event->pmu, struct perf_ibs, pmu);
+       low_nibble = value & 0xFULL;
+
+       /*
+        * This contradicts with perf_ibs_init() which allows sample period
+        * with lower nibble bits set but silently masks them off. Whereas
+        * this returns error.
+        */
+       if (low_nibble || value < perf_ibs->min_period)
+               return -EINVAL;
+
+       return 0;
+}
+
 /*
  * We need to initialize with empty group if all attributes in the
  * group are dynamic.
@@ -696,6 +718,7 @@ static struct perf_ibs perf_ibs_fetch = {
                .start          = perf_ibs_start,
                .stop           = perf_ibs_stop,
                .read           = perf_ibs_read,
+               .check_period   = perf_ibs_check_period,
        },
        .msr                    = MSR_AMD64_IBSFETCHCTL,
        .config_mask            = IBS_FETCH_MAX_CNT | IBS_FETCH_RAND_EN,
@@ -720,6 +743,7 @@ static struct perf_ibs perf_ibs_op = {
                .start          = perf_ibs_start,
                .stop           = perf_ibs_stop,
                .read           = perf_ibs_read,
+               .check_period   = perf_ibs_check_period,
        },
        .msr                    = MSR_AMD64_IBSOPCTL,
        .config_mask            = IBS_OP_MAX_CNT,