[PATCH v3] powerpc/mce: Remove per cpu variables from MCE handlers

[Nicholas Piggin]

Excerpts from Ganesh Goudar's message of January 15, 2021 10:58 pm:
> Access to per-cpu variables requires translation to be enabled on
> pseries machine running in hash mmu mode, Since part of MCE handler
> runs in realmode and part of MCE handling code is shared between ppc
> architectures pseries and powernv, it becomes difficult to manage
> these variables differently on different architectures, So have
> these variables in paca instead of having them as per-cpu variables
> to avoid complications.

Seems okay.

> 
> Maximum recursive depth of MCE is 4, Considering the maximum depth
> allowed reduce the size of event to 10 from 100.

Could you make this a separate patch, with memory saving numbers?
"Delayed" MCEs are not necessarily the same as recursive (several 
sequential MCEs can occur before the first event is processed).
But I agree 100 is pretty overboard (as is 4 recursive MCEs really).

> 
> Signed-off-by: Ganesh Goudar <ganeshgr at linux.ibm.com>
> ---
> v2: Dynamically allocate memory for machine check event info
> 
> v3: Remove check for hash mmu lpar, use memblock_alloc_try_nid
>     to allocate memory.
> ---
>  arch/powerpc/include/asm/mce.h     | 21 ++++++++-
>  arch/powerpc/include/asm/paca.h    |  4 ++
>  arch/powerpc/kernel/mce.c          | 76 +++++++++++++++++-------------
>  arch/powerpc/kernel/setup-common.c |  2 +-
>  4 files changed, 69 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
> index e6c27ae843dc..8d6e3a7a9f37 100644
> --- a/arch/powerpc/include/asm/mce.h
> +++ b/arch/powerpc/include/asm/mce.h
> @@ -204,7 +204,18 @@ struct mce_error_info {
>  	bool			ignore_event;
>  };
>  
> -#define MAX_MC_EVT	100
> +#define MAX_MC_EVT	10

> +
> +struct mce_info {
> +	int mce_nest_count;
> +	struct machine_check_event mce_event[MAX_MC_EVT];
> +	/* Queue for delayed MCE events. */
> +	int mce_queue_count;
> +	struct machine_check_event mce_event_queue[MAX_MC_EVT];
> +	/* Queue for delayed MCE UE events. */
> +	int mce_ue_count;
> +	struct machine_check_event  mce_ue_event_queue[MAX_MC_EVT];
> +};
>  
>  /* Release flags for get_mce_event() */
>  #define MCE_EVENT_RELEASE	true
> @@ -233,5 +244,13 @@ long __machine_check_early_realmode_p7(struct pt_regs *regs);
>  long __machine_check_early_realmode_p8(struct pt_regs *regs);
>  long __machine_check_early_realmode_p9(struct pt_regs *regs);
>  long __machine_check_early_realmode_p10(struct pt_regs *regs);
> +#define get_mce_info() local_paca->mce_info

I don't think this adds anything. Could you open code it?

Thanks,
Nick