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Message-ID: <CALs-HsvE9PzTrhVO0umh3KaJuLQLdk-h8sYKBg7XA4a-MXAmOg@mail.gmail.com>
Date: Wed, 10 Jul 2024 08:55:35 -0700
From: Evan Green <evan@...osinc.com>
To: Jesse Taube <jesse@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, Jonathan Corbet <corbet@....net>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
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Andrew Jones <ajones@...tanamicro.com>, Charlie Jenkins <charlie@...osinc.com>,
Xiao Wang <xiao.w.wang@...el.com>, Andy Chiu <andy.chiu@...ive.com>,
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Björn Töpel <bjorn@...osinc.com>,
Heiko Stuebner <heiko@...ech.de>, Costa Shulyupin <costa.shul@...hat.com>,
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Alexandre Ghiti <alexghiti@...osinc.com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>,
Erick Archer <erick.archer@....com>, Joel Granados <j.granados@...sung.com>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
stable@...r.kernel.org
Subject: Re: [PATCH v3 3/8] RISC-V: Check scalar unaligned access on all CPUs
On Mon, Jun 24, 2024 at 5:51 PM Jesse Taube <jesse@...osinc.com> wrote:
>
> Originally, the check_unaligned_access_emulated_all_cpus function
> only checked the boot hart. This fixes the function to check all
> harts.
>
> Fixes: 71c54b3d169d ("riscv: report misaligned accesses emulation to hwprobe")
> Signed-off-by: Jesse Taube <jesse@...osinc.com>
> Cc: stable@...r.kernel.org
> ---
> V1 -> V2:
> - New patch
> V2 -> V3:
> - Split patch
> ---
> arch/riscv/kernel/traps_misaligned.c | 23 ++++++-----------------
> 1 file changed, 6 insertions(+), 17 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index b62d5a2f4541..8fadbe00dd62 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -526,31 +526,17 @@ int handle_misaligned_store(struct pt_regs *regs)
> return 0;
> }
>
> -static bool check_unaligned_access_emulated(int cpu)
> +static void check_unaligned_access_emulated(struct work_struct *unused)
> {
> + int cpu = smp_processor_id();
> long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
> unsigned long tmp_var, tmp_val;
> - bool misaligned_emu_detected;
>
> *mas_ptr = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
>
> __asm__ __volatile__ (
> " "REG_L" %[tmp], 1(%[ptr])\n"
> : [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
> -
> - misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_EMULATED);
> - /*
> - * If unaligned_ctl is already set, this means that we detected that all
> - * CPUS uses emulated misaligned access at boot time. If that changed
> - * when hotplugging the new cpu, this is something we don't handle.
> - */
> - if (unlikely(unaligned_ctl && !misaligned_emu_detected)) {
> - pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
> - while (true)
> - cpu_relax();
> - }
This chunk was meant to detect and refuse to run on a system where a
heterogeneous CPU is hotplugged into a previously homogenous system.
The commit message doesn't mention this change, how come you
deleted it?
> -
> - return misaligned_emu_detected;
> }
>
> bool check_unaligned_access_emulated_all_cpus(void)
> @@ -562,8 +548,11 @@ bool check_unaligned_access_emulated_all_cpus(void)
> * accesses emulated since tasks requesting such control can run on any
> * CPU.
> */
> + schedule_on_each_cpu(check_unaligned_access_emulated);
> +
> for_each_online_cpu(cpu)
> - if (!check_unaligned_access_emulated(cpu))
> + if (per_cpu(misaligned_access_speed, cpu)
> + != RISCV_HWPROBE_MISALIGNED_EMULATED)
> return false;
>
> unaligned_ctl = true;
> --
> 2.45.2
>
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