Re: [PATCH v2] powerpc/mm: export current mmu mode info

[Hari Bathini <hbathini@linux.vnet.ibm.com>]

On Thursday 22 September 2016 09:32 PM, Hari Bathini wrote:
> The kernel now supports both radix and hash MMU modes. Tools like crash
> and makedumpfile need to know the current MMU mode the kernel is using,
> to debug/analyze it.  The current MMU mode depends on hardware support
> and also whether disable_radix cmdline parameter is passed to the kernel.
> The mmu_features member of cpu_spec structure holds the current MMU mode
> a cpu is using. But the above mentioned tools need to know the MMU mode
> early in their init process, when they may not have access to offset info
> of structure members. A hard-coded offset may help but it won't be robust.
>
> This patch introduces a new global variable, which holds the current MMU
> mode the kernel is running in and can be accessed by tools early in thier
> init process, helping tools to initialize accurately for each MMU mode.
> This patch also optimizes the radix_enabled() function call.
>
> Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
> ---
>
> Changes from v1:
> * Patch name changed from "ppc64/book3s: export mmu type info"
> * Optimized radix_enabled() function
>
>
>   arch/powerpc/include/asm/mmu.h      |   22 +++++++++++++++++++++-
>   arch/powerpc/kernel/machine_kexec.c |    3 +++
>   arch/powerpc/mm/hash_utils_64.c     |    2 ++
>   arch/powerpc/mm/pgtable-radix.c     |    2 ++
>   arch/powerpc/mm/pgtable.c           |    6 ++++++
>   arch/powerpc/mm/tlb_hash32.c        |    1 +
>   arch/powerpc/mm/tlb_nohash.c        |    2 ++
>   7 files changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
> index e2fb408..558987c 100644
> --- a/arch/powerpc/include/asm/mmu.h
> +++ b/arch/powerpc/include/asm/mmu.h
> @@ -199,6 +199,21 @@ static inline void mmu_clear_feature(unsigned long feature)
>
>   extern unsigned int __start___mmu_ftr_fixup, __stop___mmu_ftr_fixup;
>
> +/*
> + * Possible MMU modes
> + */
> +#define MMU_MODE_NONE           0
> +#define MMU_MODE_RADIX          1
> +#define MMU_MODE_HASH           2
> +#define MMU_MODE_HASH32         3
> +#define MMU_MODE_NOHASH         4
> +#define MMU_MODE_NOHASH32       5
> +
> +/*
> + * current MMU mode
> + */
> +extern unsigned int current_mmu_mode __read_mostly;
> +
>   #ifdef CONFIG_PPC64
>   /* This is our real memory area size on ppc64 server, on embedded, we
>    * make it match the size our of bolted TLB area
> @@ -218,7 +233,12 @@ static inline void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
>   #ifdef CONFIG_PPC_RADIX_MMU
>   static inline bool radix_enabled(void)
>   {
> -	return mmu_has_feature(MMU_FTR_TYPE_RADIX);
> +	if (current_mmu_mode == MMU_MODE_RADIX)
> +		return true;
> +	else if (current_mmu_mode != MMU_MODE_NONE)
> +		return false;
> +	else
> +		return mmu_has_feature(MMU_FTR_TYPE_RADIX);
>   }
>
>   static inline bool early_radix_enabled(void)
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index 2694d07..4ecc184 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -77,6 +77,9 @@ void arch_crash_save_vmcoreinfo(void)
>   	VMCOREINFO_SYMBOL(contig_page_data);
>   #endif
>   #if defined(CONFIG_PPC64) && defined(CONFIG_SPARSEMEM_VMEMMAP)
> +#ifdef CONFIG_PPC_BOOK3S
> +	VMCOREINFO_SYMBOL(current_mmu_mode);

Oops! This doesn't have to be under any flag. Let me resend.

Thanks
Hari