On Wed, Apr 01, 2015 at 02:30:47PM +0200, Geert Uytterhoeven wrote:
> When trying to kexec into a new kernel on a platform where multiple CPU
> cores are present, but no SMP bringup code is available yet, the
> kexec_load system call fails with:
>
> kexec_load failed: Invalid argument
>
> The SMP test added to machine_kexec_prepare() in commit 2103f6cba61a8b8b
> ("ARM: 7807/1: kexec: validate CPU hotplug support") wants to prohibit
> kexec on SMP platforms where it cannot disable secondary CPUs.
> However, this test is too strict: if the secondary CPUs couldn't be
> enabled in the first place, there's no need to disable them later at
> kexec time. Hence skip the test in the absence of SMP bringup code.
>
> This allows to add all CPU cores to the DTS from the beginning, without
> having to implement SMP bringup first, improving DT compatibility.
>
> Signed-off-by: Geert Uytterhoeven <[email protected]>
> Acked-by: Stephen Warren <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
> ---
> v2:
> - Add Acked-by.
> ---
> arch/arm/include/asm/smp_plat.h | 1 +
> arch/arm/kernel/machine_kexec.c | 3 ++-
> arch/arm/kernel/smp.c | 5 +++++
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/smp_plat.h b/arch/arm/include/asm/smp_plat.h
> index 0ad7d490ee6f2657..993e5224d8f7eeeb 100644
> --- a/arch/arm/include/asm/smp_plat.h
> +++ b/arch/arm/include/asm/smp_plat.h
> @@ -104,6 +104,7 @@ static inline u32 mpidr_hash_size(void)
> return 1 << mpidr_hash.bits;
> }
>
> +extern int platform_can_secondary_boot(void);
> extern int platform_can_cpu_hotplug(void);
>
> #endif
> diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
> index de2b085ad7535da7..8bf3b7c098881b95 100644
> --- a/arch/arm/kernel/machine_kexec.c
> +++ b/arch/arm/kernel/machine_kexec.c
> @@ -46,7 +46,8 @@ int machine_kexec_prepare(struct kimage *image)
> * and implements CPU hotplug for the current HW. If not, we won't be
> * able to kexec reliably, so fail the prepare operation.
> */
> - if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug())
> + if (num_possible_cpus() > 1 && platform_can_secondary_boot() &&
> + !platform_can_cpu_hotplug())
> return -EINVAL;
>
> /*
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 86ef244c5a24b4fa..cca5b87581855244 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -145,6 +145,11 @@ void __init smp_init_cpus(void)
> smp_ops.smp_init_cpus();
> }
>
> +int platform_can_secondary_boot(void)
> +{
> + return !!smp_ops.smp_boot_secondary;
> +}
> +
> int platform_can_cpu_hotplug(void)
> {
> #ifdef CONFIG_HOTPLUG_CPU
> --
> 1.9.1
>
> --
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