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

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Date:	Mon, 18 Nov 2013 10:16:41 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
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

> > > +/*
> > > + * 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?
> 
> Hmm, that is a problem. I will consider to export memmap according to
> what firmware provided with extra desc_version instead of using attrs from kernel
> data structure efi_memory_desc_t
> 

Matt, desc_version is already in boot_params.efi_info, so kexec-tools can get
the version from there. I do not need to export it as another file.

I think for now we do not need worry much about the compatibility issue, do you
think I need add version checking in kexec-tools currently? like below?

if (desc_version != 1) /* current version is 1? */
	error out it is not supported

--
Thanks
Dave
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