linux-kernel - Re: [PATCH 2/5] riscv: cpu_ops_spinwait: Support for 64bit hartid

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Date:   Thu, 26 May 2022 15:45:50 +0530
From:   Sunil V L <sunilvl@...tanamicro.com>
To:     Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, Sunil V L <sunil.vl@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH 2/5] riscv: cpu_ops_spinwait: Support for 64bit hartid

On Wed, May 25, 2022 at 05:27:51PM +0200, Heinrich Schuchardt wrote:
> On 5/25/22 17:11, Sunil V L wrote:
> > The hartid can be a 64bit value on RV64 platforms. This patch modifies
> > the hartid variable type to unsigned long so that it can hold 64bit
> > value on RV64 platforms.
> > 
> > Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> > ---
> >   arch/riscv/kernel/cpu_ops_spinwait.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c
> > index 346847f6c41c..51ac07514a62 100644
> > --- a/arch/riscv/kernel/cpu_ops_spinwait.c
> > +++ b/arch/riscv/kernel/cpu_ops_spinwait.c
> > @@ -18,7 +18,7 @@ void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data");
> >   static void cpu_update_secondary_bootdata(unsigned int cpuid,
> >   				   struct task_struct *tidle)
> >   {
> > -	int hartid = cpuid_to_hartid_map(cpuid);
> > +	unsigned long hartid = cpuid_to_hartid_map(cpuid);
> >   	/*
> >   	 * The hartid must be less than NR_CPUS to avoid out-of-bound access
> 
> This line follows:
> 
> if (hartid == INVALID_HARTID || hartid >= NR_CPUS)
> 
> INVALID_HARTID is defined as ULONG_MAX. Please, mention that you are fixing
> a bug:
> 
> Fixes: c78f94f35cf648 ("RISC-V: Use __cpu_up_stack/task_pointer only for
> spinwait method")
> 
> NR_CPUS alias CONFIG_NR_CPUS is an int. You should convert it to unsigned
> before comparing it to hartid to avoid build warnings.

Thank you for the feedback. Have modified the patch and commit message
as per your suggestion in V2 version. Please check.

Thanks
Sunil
> 
> Best regards
> 
> Heinrich
>