[linux-yocto] [PATCH 2/3] meta: efi-ext.cfg: replace EFI_VARS with EFIVAR_FS

[Stanacar, StefanX]

On Wed, 2014-03-12 at 23:15 -0400, Bruce Ashfield wrote:
> On 2014-03-12, 10:15 AM, Stefan Stanacar wrote:
> > Linux kernel exposes EFI variables data to userspace via 2 interfaces:
> > - old sysfs-efivars interface (CONFIG_EFI_VARS), populated at /sys/firmware/efi/vars,
> > 1024 byte maximum per-variable data size limitation, no UEFI Secure Boot variables support
> > and not recommended anymore.
> > - new efivarfs interface (CONFIG_EFIVAR_FS), typically mounted like this:
> > mount -t efivarfs efivarfs /sys/firmware/efi/efivar
> > It was added in 3.8 intended as a replacement for the sysfs-efivars interface,
> > has no maximum per-variable size limitation and supports UEFI Secure Boot variables.
> > It also allows creating new vars easily, a very useful trick:
> > printf "\x07\x00\x00\x00\x00" > /sys/firmware/efi/efivar/myvar-12345678-1234-1234-1234-123456789abc
> 
> I haven't looked into it yet, so I'll ask, can both co-exist ? Or
> is the most common mount point going to cause problems with a
> a conflicting path ?
> 

They both can co-exist - but from what I've read they shouldn't both be
active / mounted (the problem isn't the mount point but data
inconsistency). So I think we can safely enable both as modules.
Can the new one be in efi.cfg and the old one stays in efi-ext.cfg?

"Both the
sysfs and efivarfs code maintain their own lists which means the two
interfaces can be running simultaneously without interference, though
it should be noted that because no synchronisation is performed it is
very easy to create inconsistencies. efibootmgr doesn't currently use
efivarfs and users are likely to also require the old sysfs interface,
so it makes sense to allow both to be built."
from:
https://lkml.org/lkml/2013/4/16/473


Cheers,
Stefan

> If so, I'd rather introduce the new one, and keep the old one
> around for this 1.6 release, that way I can warn and remove the
> existing one.
> 
> Cheers,
> 
> Bruce
> 
> >
> > Signed-off-by: Stefan Stanacar <stefanx.stanacar at intel.com>
> > ---
> >   meta/cfg/kernel-cache/cfg/efi-ext.cfg | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/meta/cfg/kernel-cache/cfg/efi-ext.cfg b/meta/cfg/kernel-cache/cfg/efi-ext.cfg
> > index 6371da2..edceb75 100644
> > --- a/meta/cfg/kernel-cache/cfg/efi-ext.cfg
> > +++ b/meta/cfg/kernel-cache/cfg/efi-ext.cfg
> > @@ -10,5 +10,5 @@ CONFIG_PARTITION_ADVANCED=y
> >   # Add support for optional EFI features
> >   CONFIG_FRAMEBUFFER_CONSOLE=y
> >   CONFIG_FB_EFI=y
> > -CONFIG_EFI_VARS=y
> > +CONFIG_EFIVAR_FS=y
> >   CONFIG_EFI_PARTITION=y
> >
>