linux-kernel - [PATCH 6.0 057/862] RISC-V: Re-enable counter access from userspace

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Message-Id: <20221019083252.507436677@linuxfoundation.org>
Date:   Wed, 19 Oct 2022 10:22:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Conor Dooley <conor.dooley@...rochip.com>,
        Palmer Dabbelt <palmer@...osinc.com>
Subject: [PATCH 6.0 057/862] RISC-V: Re-enable counter access from userspace

From: Palmer Dabbelt <palmer@...osinc.com>

commit 5a5294fbe0200d1327f0e089135dad77b45aa2ee upstream.

These counters were part of the ISA when we froze the uABI, removing
them breaks userspace.

Link: https://lore.kernel.org/all/YxEhC%2FmDW1lFt36J@aurel32.net/
Fixes: e9991434596f ("RISC-V: Add perf platform driver based on SBI PMU extension")
Tested-by: Conor Dooley <conor.dooley@...rochip.com>
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
Link: https://lore.kernel.org/r/20220928131807.30386-1-palmer@rivosinc.com
Cc: stable@...r.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/perf/riscv_pmu_sbi.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -645,8 +645,11 @@ static int pmu_sbi_starting_cpu(unsigned
 	struct riscv_pmu *pmu = hlist_entry_safe(node, struct riscv_pmu, node);
 	struct cpu_hw_events *cpu_hw_evt = this_cpu_ptr(pmu->hw_events);
 
-	/* Enable the access for TIME csr only from the user mode now */
-	csr_write(CSR_SCOUNTEREN, 0x2);
+	/*
+	 * Enable the access for CYCLE, TIME, and INSTRET CSRs from userspace,
+	 * as is necessary to maintain uABI compatibility.
+	 */
+	csr_write(CSR_SCOUNTEREN, 0x7);
 
 	/* Stop all the counters so that they can be enabled from perf */
 	pmu_sbi_stop_all(pmu);