Re: [PATCH v5 12/31] powernv/fadump: register kernel metadata address with opal

[Michael Ellerman <mpe@ellerman.id.au>]

Hari Bathini <hbathini@linux.ibm.com> writes:
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index b8061fb9..a086a09 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -283,17 +286,17 @@ static void __init fadump_reserve_crash_area(unsigned long base,
>  
>  int __init fadump_reserve_mem(void)
>  {
> +	int ret = 1;
>  	unsigned long base, size, memory_boundary;

Please try to use reverse christmas tree style when possible.

> @@ -363,29 +366,43 @@ int __init fadump_reserve_mem(void)
>  		 * use memblock_find_in_range() here since it doesn't allocate
>  		 * from bottom to top.
>  		 */
> -		for (base = fw_dump.boot_memory_size;
> -		     base <= (memory_boundary - size);
> -		     base += size) {
> +		while (base <= (memory_boundary - size)) {
>  			if (memblock_is_region_memory(base, size) &&
>  			    !memblock_is_region_reserved(base, size))
>  				break;
> +
> +			base += size;
>  		}

Some of these changes look like they might not be necessary in this
patch, ie. could be split out into a lead-up patch. eg. the conversion
from for to while. But it's a bit hard to tell.

> diff --git a/arch/powerpc/platforms/powernv/opal-fadump.c b/arch/powerpc/platforms/powernv/opal-fadump.c
> index e330877..e5c4700 100644
> --- a/arch/powerpc/platforms/powernv/opal-fadump.c
> +++ b/arch/powerpc/platforms/powernv/opal-fadump.c
> @@ -13,14 +13,86 @@
>  #include <linux/seq_file.h>
>  #include <linux/of_fdt.h>
>  #include <linux/libfdt.h>
> +#include <linux/mm.h>
>  
> +#include <asm/page.h>
>  #include <asm/opal.h>
>  
>  #include "../../kernel/fadump-common.h"
> +#include "opal-fadump.h"
> +
> +static struct opal_fadump_mem_struct *opal_fdm;
> +
> +/* Initialize kernel metadata */
> +static void opal_fadump_init_metadata(struct opal_fadump_mem_struct *fdm)
> +{
> +	fdm->version = OPAL_FADUMP_VERSION;
> +	fdm->region_cnt = 0;
> +	fdm->registered_regions = 0;
> +	fdm->fadumphdr_addr = 0;
> +}
>  
>  static ulong opal_fadump_init_mem_struct(struct fw_dump *fadump_conf)
>  {
> -	return fadump_conf->reserve_dump_area_start;
> +	ulong addr = fadump_conf->reserve_dump_area_start;

I just noticed you're using ulong, which I haven't seen much before. KVM
uses it a lot but not much else.

Because this is all 64-bit only code I'd probably rather you just use
u64 explicitly to avoid anyone having to think about it.

> +
> +	opal_fdm = __va(fadump_conf->kernel_metadata);
> +	opal_fadump_init_metadata(opal_fdm);
> +
> +	opal_fdm->region_cnt = 1;
> +	opal_fdm->rgn[0].src	= RMA_START;
> +	opal_fdm->rgn[0].dest	= addr;
> +	opal_fdm->rgn[0].size	= fadump_conf->boot_memory_size;
> +	addr += fadump_conf->boot_memory_size;
> +
> +	/*
> +	 * Kernel metadata is passed to f/w and retrieved in capture kerenl.
> +	 * So, use it to save fadump header address instead of calculating it.
> +	 */
> +	opal_fdm->fadumphdr_addr = (opal_fdm->rgn[0].dest +
> +				    fadump_conf->boot_memory_size);
> +
> +	return addr;
> +}
> +
> +static ulong opal_fadump_get_metadata_size(void)
> +{
> +	ulong size = sizeof(struct opal_fadump_mem_struct);
> +
> +	size = PAGE_ALIGN(size);
> +	return size;

	return PAGE_ALIGN(sizeof(struct opal_fadump_mem_struct));

???

> diff --git a/arch/powerpc/platforms/powernv/opal-fadump.h b/arch/powerpc/platforms/powernv/opal-fadump.h
> new file mode 100644
> index 0000000..19cac1f
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/opal-fadump.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Firmware-Assisted Dump support on POWER platform (OPAL).
> + *
> + * Copyright 2019, IBM Corp.
> + * Author: Hari Bathini <hbathini@linux.ibm.com>
> + */
> +
> +#ifndef __PPC64_OPAL_FA_DUMP_H__
> +#define __PPC64_OPAL_FA_DUMP_H__

Usual style is _ASM_POWERPC_OPAL_FADUMP_H.


> +/* OPAL FADump structure format version */
> +#define OPAL_FADUMP_VERSION			0x1

What is the meaning of this version? How/can we change it. What does it
mean if it's a different number? Please provide some comments or doco
describing how it's expected to be used.

We're defining some sort of ABI here and I want to understand/have
better documentation on what the implications of that are.

> diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.c b/arch/powerpc/platforms/pseries/rtas-fadump.c
> index 2b94392..4111ee9 100644
> --- a/arch/powerpc/platforms/pseries/rtas-fadump.c
> +++ b/arch/powerpc/platforms/pseries/rtas-fadump.c
> @@ -121,6 +121,21 @@ static ulong rtas_fadump_init_mem_struct(struct fw_dump *fadump_conf)
>  	return addr;
>  }
>  
> +/*
> + * On this platform, the metadata struture is passed while registering
> + * for FADump and the same is returned by f/w in capture kernel.
> + * No additional provision to setup kernel metadata separately.
> + */
> +static ulong rtas_fadump_get_metadata_size(void)
> +{
> +	return 0;
> +}
> +
> +static int rtas_fadump_setup_metadata(struct fw_dump *fadump_conf)
> +{
> +	return 0;
> +}

Each of these uses about 16 byes of text as well as space in the symbol
table. I think there's only one call site for each, so allowing the
callback to be NULL and skipping the call when it is would be slightly
more efficient.


> @@ -486,9 +501,10 @@ static void rtas_fadump_trigger(struct fadump_crash_info_header *fdh,
>  	rtas_os_term((char *)msg);
>  }
>  
> -
>  static struct fadump_ops rtas_fadump_ops = {
>  	.fadump_init_mem_struct		= rtas_fadump_init_mem_struct,
> +	.fadump_get_metadata_size	= rtas_fadump_get_metadata_size,
> +	.fadump_setup_metadata		= rtas_fadump_setup_metadata,
>  	.fadump_register		= rtas_fadump_register,
>  	.fadump_unregister		= rtas_fadump_unregister,
>  	.fadump_invalidate		= rtas_fadump_invalidate,

cheers