Re: [PATCH v2 1/5] powerpc/powernv: Re-enable imc trace-mode in kernel

[maddy <maddy@linux.ibm.com>]

On 1/21/20 3:47 PM, Anju T Sudhakar wrote:
> commit <249fad734a25> ""powerpc/perf: Disable trace_imc pmu"
> disables IMC(In-Memory Collection) trace-mode in kernel, since frequent
> mode switching between accumulation mode and trace mode via the spr LDBAR
> in the hardware can trigger a checkstop(system crash).
>
> Patch to re-enable imc-trace mode in kernel.
>
> The following patch in this series will address the mode switching issue
> by implementing a global lock, and will restrict the usage of
> accumulation and trace-mode at a time.

Reviewed-by: MAdhavan Srinivasan <maddy@linux.ibm.com>

>
> Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
> ---
>   arch/powerpc/platforms/powernv/opal-imc.c | 9 +--------
>   1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
> index 000b350d4060..3b4518f4b643 100644
> --- a/arch/powerpc/platforms/powernv/opal-imc.c
> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
> @@ -278,14 +278,7 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
>   			domain = IMC_DOMAIN_THREAD;
>   			break;
>   		case IMC_TYPE_TRACE:
> -			/*
> -			 * FIXME. Using trace_imc events to monitor application
> -			 * or KVM thread performance can cause a checkstop
> -			 * (system crash).
> -			 * Disable it for now.
> -			 */
> -			pr_info_once("IMC: disabling trace_imc PMU\n");
> -			domain = -1;
> +			domain = IMC_DOMAIN_TRACE;
>   			break;
>   		default:
>   			pr_warn("IMC Unknown Device type \n");