linux-kernel - [PATCH 2/2] drivers/perf: riscv: Do not allow invalid raw event config

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Message-Id: <20241209-pmu_event_fixes-v1-2-d9525e90072c@rivosinc.com>
Date: Mon, 09 Dec 2024 16:04:46 -0800
From: Atish Patra <atishp@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Atish Patra <atishp@...shpatra.org>, 
 Anup Patel <anup@...infault.org>, Will Deacon <will@...nel.org>, 
 Mark Rutland <mark.rutland@....com>, 
 Mayuresh Chitale <mchitale@...tanamicro.com>, 
 Samuel Holland <samuel.holland@...ive.com>
Cc: Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Atish Patra <atishp@...osinc.com>
Subject: [PATCH 2/2] drivers/perf: riscv: Do not allow invalid raw event
 config

The SBI specification allows only lower 48bits of hpmeventX to be
configured via SBI PMU. Currently, the driver masks of the higher
bits but doesn't return an error. This will lead to an additional
SBI call for config matching which should return for an invalid
event error in most of the cases.

However, if a platform(i.e Rocket and sifive cores) implements a
bitmap of all bits in the event encoding this will lead to an
incorrect event being programmed leading to user confusion.

Report the error to the user if higher bits are set during the
event mapping itself to avoid the confusion and save an additional
SBI call.

Suggested-by: Samuel Holland <samuel.holland@...ive.com>
Signed-off-by: Atish Patra <atishp@...osinc.com>
---
 drivers/perf/riscv_pmu_sbi.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 3473ba02abf3..fb6eda90f771 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -507,7 +507,7 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 {
 	u32 type = event->attr.type;
 	u64 config = event->attr.config;
-	int ret;
+	int ret = -ENOENT;
 
 	/*
 	 * Ensure we are finished checking standard hardware events for
@@ -536,8 +536,11 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 
 		switch (config >> 62) {
 		case 0:
-			ret = RISCV_PMU_RAW_EVENT_IDX;
-			*econfig = config & RISCV_PMU_RAW_EVENT_MASK;
+			/* Return error any bits [48-63] is set  as it is not allowed by the spec */
+			if (!(config & ~RISCV_PMU_RAW_EVENT_MASK)) {
+				*econfig = config & RISCV_PMU_RAW_EVENT_MASK;
+				ret = RISCV_PMU_RAW_EVENT_IDX;
+			}
 			break;
 		case 2:
 			ret = (config & 0xFFFF) | (SBI_PMU_EVENT_TYPE_FW << 16);
@@ -554,7 +557,6 @@ static int pmu_sbi_event_map(struct perf_event *event, u64 *econfig)
 		}
 		break;
 	default:
-		ret = -ENOENT;
 		break;
 	}
 

-- 
2.34.1