linux-kernel - Re: [patch 5/7 v2] export efi runtime memory mapping to sysfs

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Message-ID: <20131113155027.GC17248@console-pimps.org>
Date:	Wed, 13 Nov 2013 15:50:27 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	dyoung@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	x86@...nel.org, mjg59@...f.ucam.org, hpa@...or.com,
	James.Bottomley@...senPartnership.com, vgoyal@...hat.com,
	ebiederm@...ssion.com, horms@...ge.net.au,
	kexec@...ts.infradead.org, bp@...en8.de
Subject: Re: [patch 5/7 v2] export efi runtime memory mapping to sysfs

On Tue, 05 Nov, at 04:20:12PM, dyoung@...hat.com wrote:
> kexec kernel will need exactly same mapping for
> efi runtime memory ranges. Thus here export the
> runtime ranges mapping to sysfs, kexec-tools
> will assemble them and pass to 2nd kernel via
> setup_data.
> 
> Introducing a new directly /sys/firmware/efi/efi-runtime-map
> Just like /sys/firmware/memmap. Containing below attribute
> in each file of that directory:
> attribute  num_pages  phys_addr  type  virt_addr
> 
> It will not work for efi 32bit. Only x86_64 currently.
> 
> Signed-off-by: Dave Young <dyoung@...hat.com>
> ---
>  Documentation/ABI/testing/sysfs-efi-runtime-map |   45 ++++++
>  arch/x86/include/asm/efi.h                      |    3 
>  arch/x86/platform/efi/efi.c                     |   11 +
>  drivers/firmware/efi/Kconfig                    |   10 +
>  drivers/firmware/efi/Makefile                   |    1 
>  drivers/firmware/efi/efi-runtime-map.c          |  164 ++++++++++++++++++++++++
>  drivers/firmware/efi/efi.c                      |    3 
>  include/linux/efi.h                             |    6 
>  8 files changed, 242 insertions(+), 1 deletion(-)

[...]

> @@ -852,6 +855,14 @@ static void efi_map_regions(void **new_m
>  
>  		memcpy(*new_memmap + (*count * memmap.desc_size), md,
>  		       memmap.desc_size);
> +		if (md->type != EFI_BOOT_SERVICES_CODE &&
> +			md->type != EFI_BOOT_SERVICES_DATA) {
> +			efi_runtime_map = krealloc(efi_runtime_map,
> +					(nr_efi_runtime_map + 1) *
> +					sizeof(efi_memory_desc_t), GFP_KERNEL);
> +			*(efi_runtime_map + nr_efi_runtime_map) = *md;
> +			nr_efi_runtime_map++;
> +		}
>  		(*count)++;
>  	}

You really need to be using 'memmap.desc_size' here and not
sizeof(efi_memory_desc_t) as the two may differ. Also, you should be
checking for failure of krealloc() and using memcpy() instead of
directly dereferencing 'md'.

> --- linux-2.6.orig/drivers/firmware/efi/Makefile
> +++ linux-2.6/drivers/firmware/efi/Makefile
> @@ -4,3 +4,4 @@
>  obj-y					+= efi.o vars.o
>  obj-$(CONFIG_EFI_VARS)			+= efivars.o
>  obj-$(CONFIG_EFI_VARS_PSTORE)		+= efi-pstore.o
> +obj-$(CONFIG_EFI_RUNTIME_MAP)		+= efi-runtime-map.o
> --- /dev/null
> +++ linux-2.6/drivers/firmware/efi/efi-runtime-map.c

Small nit but I wouldn't bother prefixing the filename with "efi-",
since you can't build this file as a module.

> +/*
> + * These are default attributes that are added for every memmap entry.
> + */
> +static struct attribute *def_attrs[] = {
> +	&map_type_attr.attr,
> +	&map_phys_addr_attr.attr,
> +	&map_virt_addr_attr.attr,
> +	&map_num_pages_attr.attr,
> +	&map_attribute_attr.attr,
> +	NULL
> +};

If the UEFI spec ever releases an update for the memory descriptor
structure, and bumps 'memmap.desc_version', how are we going to signal
the incompatibility to legacy versions of kexec tools?

-- 
Matt Fleming, Intel Open Source Technology Center
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