[Skiboot] [RFC PATCH] opal/xstop: Use nvram param to enable/disable sw checkstop.

[ppaidipe]

Hi Mahesh

On 2017-12-14 21:06, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> 
> Add a mechanism to enable/disable sw checkstop by looking at nvram 
> option
> opal-sw-xstop=<enable/disable>.
> 
> For now this patch disables the sw checkstop trigger unless explicitly
> enabled through nvram option 'opal-sw-xstop=enable'. This will allow an
> opportunity to get host kernel in panic path or xmon for unrecoverable
> HMIs or MCE, to be able to debug the issue effectively.

It will be good to enable by default, and let's give control to user to 
disable
the sw-xstop using nvram option. Otherwise all test infrastructures will 
break.

Thanks
Pridhiviraj

> 
> To enable sw checkstop in opal issue following command:
> 
> # nvram -p ibm,skiboot --update-config opal-sw-xstop=enable
> 
> NOTE: This is a workaround patch to disable sw checkstop by default to 
> gain
> control in host kernel for better checkstop debugging. Once we have 
> most of
> the checkstop issues stabilized/resolved, revisit this patch to enable 
> sw
> checkstop by default.
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> ---
>  hw/xscom.c |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/hw/xscom.c b/hw/xscom.c
> index de5a27e..4d3d88f 100644
> --- a/hw/xscom.c
> +++ b/hw/xscom.c
> @@ -24,6 +24,7 @@
>  #include <errorlog.h>
>  #include <opal-api.h>
>  #include <timebase.h>
> +#include <nvram.h>
> 
>  /* Mask of bits to clear in HMER before an access */
>  #define HMER_CLR_MASK	(~(SPR_HMER_XSCOM_FAIL | \
> @@ -827,6 +828,18 @@ int64_t xscom_trigger_xstop(void)
>  {
>  	int rc = OPAL_UNSUPPORTED;
> 
> +	/*
> +	 * Workaround until we iron out all checkstop issues at present.
> +	 *
> +	 * By deafult do not trigger sw checkstop unless explicitly enabled
> +	 * through nvram option 'opal-sw-xstop=enable'.
> +	 *
> +	 * NOTE: Once all checkstop issues are resolved/stabilized reverse
> +	 * the logic to enable sw checkstop by default.
> +	 */
> +	if (!nvram_query_eq("opal-sw-xstop", "enable"))
> +		return rc;
> +
>  	if (xstop_xscom.addr)
>  		rc = xscom_writeme(xstop_xscom.addr,
>  				PPC_BIT(xstop_xscom.fir_bit));
> 
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