Re: [PATCH v2] powerpc/kernel/sysfs: Export ldbar spr to sysfs

From: Michael Ellerman
Date: Tue Oct 31 2017 - 20:50:12 EST


Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx> writes:

> Add ldbar spr to sysfs. The spr will hold thread level In-Memory Collection (IMC)
> counter configuration data.

This is missing any justification for why we would want to expose this,
and in particular why we would make it *writable*.

cheers

> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index 4437c70..f8caee0 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -485,6 +485,7 @@ SYSFS_PMCSETUP(mmcra, SPRN_MMCRA);
> SYSFS_SPRSETUP(purr, SPRN_PURR);
> SYSFS_SPRSETUP(spurr, SPRN_SPURR);
> SYSFS_SPRSETUP(pir, SPRN_PIR);
> +SYSFS_SPRSETUP(ldbar, SPRN_LDBAR);
>
> /*
> Lets only enable read for phyp resources and
> @@ -492,6 +493,7 @@ SYSFS_SPRSETUP(pir, SPRN_PIR);
> Lets be conservative and default to pseries.
> */
> static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
> +static DEVICE_ATTR(ldbar, 0600, show_ldbar, store_ldbar);
> static DEVICE_ATTR(spurr, 0400, show_spurr, NULL);
> static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
> static DEVICE_ATTR(pir, 0400, show_pir, NULL);
> @@ -757,6 +759,9 @@ static int register_cpu_online(unsigned int cpu)
> device_create_file(s, &pmc_attrs[i]);
>
> #ifdef CONFIG_PPC64
> + if (cpu_has_feature(CPU_FTR_ARCH_300))
> + device_create_file(s, &dev_attr_ldbar);
> +
> if (cpu_has_feature(CPU_FTR_MMCRA))
> device_create_file(s, &dev_attr_mmcra);
>
> @@ -842,6 +847,9 @@ static int unregister_cpu_online(unsigned int cpu)
> device_remove_file(s, &pmc_attrs[i]);
>
> #ifdef CONFIG_PPC64
> + if (cpu_has_feature(CPU_FTR_ARCH_300))
> + device_remove_file(s, &dev_attr_ldbar);
> +
> if (cpu_has_feature(CPU_FTR_MMCRA))
> device_remove_file(s, &dev_attr_mmcra);
>
> --
> 2.7.4