[PATCH v4 14/25] powernv/fadump: process the crashdump by exporting it as /proc/vmcore

[Mahesh J Salgaonkar]

On 2019-07-16 17:03:38 Tue, Hari Bathini wrote:
> Add support in the kernel to process the crash'ed kernel's memory
> preserved during MPIPL and export it as /proc/vmcore file for the
> userland scripts to filter and analyze it later.
> 
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>  arch/powerpc/platforms/powernv/opal-fadump.c |  190 ++++++++++++++++++++++++++
>  1 file changed, 187 insertions(+), 3 deletions(-)
> 
[...]
> +		ret = opal_mpipl_query_tag(OPAL_MPIPL_TAG_KERNEL, &addr);
> +		if ((ret != OPAL_SUCCESS) || !addr) {
> +			pr_err("Failed to get Kernel metadata (%lld)\n", ret);
> +			return 1;
> +		}
> +
> +		addr = be64_to_cpu(addr);
> +		pr_debug("Kernel metadata addr: %llx\n", addr);
> +
> +		opal_fdm_active = __va(addr);
> +		r_opal_fdm_active = (void *)addr;
> +		if (r_opal_fdm_active->version != OPAL_FADUMP_VERSION) {
> +			pr_err("FADump active but version (%u) unsupported!\n",
> +			       r_opal_fdm_active->version);
> +			return 1;
> +		}
> +
> +		/* Kernel regions not registered with f/w  for MPIPL */
> +		if (r_opal_fdm_active->registered_regions == 0) {
> +			opal_fdm_active = NULL;

What about partial dump capture scenario ? What if opal crashes while
kernel was in middle of registering ranges ? We may have partial dump
captured which won't be useful.
e,g. If we have total of 4 ranges to be registered and opal crashes
after successful registration of only 2 ranges with 2 pending, we will get a
partial dump which needs to be ignored.

I think check shuold be comparing registered_regions against total number of
regions. What do you think ?

Thanks,
-Mahesh.

> +			return 1;
> +		}
> +
> +		pr_info("Firmware-assisted dump is active.\n");
> +		fadump_conf->dump_active = 1;
> +		opal_fadump_get_config(fadump_conf, r_opal_fdm_active);
> +	}
> +
>  	return 1;
>  }
> 

-- 
Mahesh J Salgaonkar