linux-kernel - Re: [PATCH v2] perf: RISCV: Fix panic on pmu overflow handler

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Date: Wed, 28 Feb 2024 00:02:13 -0800
From: Atish Patra <atishp@...osinc.com>
To: Fei Wu <fei2.wu@...el.com>, atishp@...shpatra.org, anup@...infault.org,
 paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Alexandre Ghiti <alex@...ti.fr>
Subject: Re: [PATCH v2] perf: RISCV: Fix panic on pmu overflow handler

On 2/27/24 21:38, Fei Wu wrote:
> (1 << idx) of int is not desired when setting bits in unsigned long
> overflowed_ctrs, use BIT() instead. This panic happens when running
> 'perf record -e branches' on sophgo sg2042.
> 
> [  273.311852] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000098
> [  273.320851] Oops [#1]
> [  273.323179] Modules linked in:
> [  273.326303] CPU: 0 PID: 1475 Comm: perf Not tainted 6.6.0-rc3+ #9
> [  273.332521] Hardware name: Sophgo Mango (DT)
> [  273.336878] epc : riscv_pmu_ctr_get_width_mask+0x8/0x62
> [  273.342291]  ra : pmu_sbi_ovf_handler+0x2e0/0x34e
> [  273.347091] epc : ffffffff80aecd98 ra : ffffffff80aee056 sp : fffffff6e36928b0
> [  273.354454]  gp : ffffffff821f82d0 tp : ffffffd90c353200 t0 : 0000002ade4f9978
> [  273.361815]  t1 : 0000000000504d55 t2 : ffffffff8016cd8c s0 : fffffff6e3692a70
> [  273.369180]  s1 : 0000000000000020 a0 : 0000000000000000 a1 : 00001a8e81800000
> [  273.376540]  a2 : 0000003c00070198 a3 : 0000003c00db75a4 a4 : 0000000000000015
> [  273.383901]  a5 : ffffffd7ff8804b0 a6 : 0000000000000015 a7 : 000000000000002a
> [  273.391327]  s2 : 000000000000ffff s3 : 0000000000000000 s4 : ffffffd7ff8803b0
> [  273.398773]  s5 : 0000000000504d55 s6 : ffffffd905069800 s7 : ffffffff821fe210
> [  273.406139]  s8 : 000000007fffffff s9 : ffffffd7ff8803b0 s10: ffffffd903f29098
> [  273.413660]  s11: 0000000080000000 t3 : 0000000000000003 t4 : ffffffff8017a0ca
> [  273.421022]  t5 : ffffffff8023cfc2 t6 : ffffffd9040780e8
> [  273.426437] status: 0000000200000100 badaddr: 0000000000000098 cause: 000000000000000d
> [  273.434512] [<ffffffff80aecd98>] riscv_pmu_ctr_get_width_mask+0x8/0x62
> [  273.441169] [<ffffffff80076bd8>] handle_percpu_devid_irq+0x98/0x1ee
> [  273.447562] [<ffffffff80071158>] generic_handle_domain_irq+0x28/0x36
> [  273.454151] [<ffffffff8047a99a>] riscv_intc_irq+0x36/0x4e
> [  273.459659] [<ffffffff80c944de>] handle_riscv_irq+0x4a/0x74
> [  273.465442] [<ffffffff80c94c48>] do_irq+0x62/0x92
> [  273.470360] Code: 0420 60a2 6402 5529 0141 8082 0013 0000 0013 0000 (6d5c) b783
> [  273.477921] ---[ end trace 0000000000000000 ]---
> [  273.482630] Kernel panic - not syncing: Fatal exception in interrupt
> 
> Signed-off-by: Fei Wu <fei2.wu@...el.com>
> ---
>   drivers/perf/riscv_pmu_sbi.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> index 16acd4dcdb96..335171db9647 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -731,14 +731,14 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
>   		/* compute hardware counter index */
>   		hidx = info->csr - CSR_CYCLE;
>   		/* check if the corresponding bit is set in sscountovf */
> -		if (!(overflow & (1 << hidx)))
> +		if (!(overflow & BIT(hidx)))
>   			continue;
>   
>   		/*
>   		 * Keep a track of overflowed counters so that they can be started
>   		 * with updated initial value.
>   		 */
> -		overflowed_ctrs |= 1 << lidx;
> +		overflowed_ctrs |= BIT(lidx);
>   		hw_evt = &event->hw;
>   		riscv_pmu_event_update(event);
>   		perf_sample_data_init(&data, 0, hw_evt->last_period);

Thanks for the fix.Can you modify the other two instance of 1<< as 
pointed by Alex as well. They are harmless because 32 counters supported 
at max but improves the code quality.
With that:
Reviewed-by: Atish Patra <atishp@...osinc.com>