linux-kernel - Re: [PATCH] powerpc/4xx: Fix setup

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Date:   Tue, 29 Jun 2021 21:58:45 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/4xx: Fix setup_kuep() on SMP

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> On SMP, setup_kuep() is also called from start_secondary() since
> commit 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
>
> start_secondary() is not an __init function.
>
> Remove the __init marker from setup_kuep() and bail out when
> not caller on the first CPU as the work is already done.
>
> Reported-by: kernel test robot <lkp@...el.com>
> Fixes: 10248dcba120 ("powerpc/44x: Implement Kernel Userspace Exec Protection (KUEP)")
> Fixes: 86f46f343272 ("powerpc/32s: Initialise KUAP and KUEP in C").
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/mm/nohash/44x.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/nohash/44x.c b/arch/powerpc/mm/nohash/44x.c
> index 7da6d1e9fc9b..20c18bd5b9a0 100644
> --- a/arch/powerpc/mm/nohash/44x.c
> +++ b/arch/powerpc/mm/nohash/44x.c
> @@ -241,8 +241,11 @@ void __init mmu_init_secondary(int cpu)
>  #endif /* CONFIG_SMP */
>  
>  #ifdef CONFIG_PPC_KUEP
> -void __init setup_kuep(bool disabled)
> +void setup_kuep(bool disabled)
>  {
> +	if (smp_processor_id() != boot_cpuid)
> +		return;
> +
>  	if (disabled)
>  		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));
>  	else

Building ppc44x_defconfig gives me:

  /linux/arch/powerpc/mm/nohash/44x.c: In function 'setup_kuep':
  /linux/arch/powerpc/mm/nohash/44x.c:246:35: error: 'boot_cpuid' undeclared (first use in this function); did you mean 'boot_cpu_init'?
    246 |         if (smp_processor_id() != boot_cpuid)
        |                                   ^~~~~~~~~~
        |                                   boot_cpu_init
  /linux/arch/powerpc/mm/nohash/44x.c:246:35: note: each undeclared identifier is reported only once for each function it appears in

cheers