6.12-stable review patch. If anyone has any objections, please let me know.
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From: Ravi Bangoria ravi.bangoria@amd.com
[ Upstream commit 598bdf4fefff5af4ce6d26d16f7b2a20808fc4cb ]
Instead of using standard perf_event_attr->freq=0 and ->sample_period fields, IBS event in 'sample period mode' can also be opened by setting period value directly in perf_event_attr->config in a MaxCnt bit-field format.
IBS OP MaxCnt bits are defined as:
(high bits) IbsOpCtl[26:20] = IbsOpMaxCnt[26:20] (low bits) IbsOpCtl[15:0] = IbsOpMaxCnt[19:4]
Perf event sample period can be derived from MaxCnt bits as:
sample_period = (high bits) | ((low_bits) << 4);
However, current code just masks MaxCnt bits and shifts all of them, including high bits, which is incorrect. Fix it.
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/20250115054438.1021-4-ravi.bangoria@amd.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/events/amd/ibs.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c index 8f3b5764e139d..d34ee6f04f18f 100644 --- a/arch/x86/events/amd/ibs.c +++ b/arch/x86/events/amd/ibs.c @@ -272,7 +272,7 @@ static int perf_ibs_init(struct perf_event *event) { struct hw_perf_event *hwc = &event->hw; struct perf_ibs *perf_ibs; - u64 max_cnt, config; + u64 config; int ret;
perf_ibs = get_ibs_pmu(event->attr.type); @@ -309,10 +309,19 @@ static int perf_ibs_init(struct perf_event *event) if (!hwc->sample_period) hwc->sample_period = 0x10; } else { - max_cnt = config & perf_ibs->cnt_mask; + u64 period = 0; + + if (perf_ibs == &perf_ibs_op) { + period = (config & IBS_OP_MAX_CNT) << 4; + if (ibs_caps & IBS_CAPS_OPCNTEXT) + period |= config & IBS_OP_MAX_CNT_EXT_MASK; + } else { + period = (config & IBS_FETCH_MAX_CNT) << 4; + } + config &= ~perf_ibs->cnt_mask; - event->attr.sample_period = max_cnt << 4; - hwc->sample_period = event->attr.sample_period; + event->attr.sample_period = period; + hwc->sample_period = period; }
if (!hwc->sample_period)