Bug#773309: CONFIG_PSTORE not enabled for arm64
Control: severity -1 wishlist
On Wed, 2014-12-17 at 16:30 +0000, Leif Lindholm wrote:
> On Wed, Dec 17, 2014 at 02:57:17PM +0000, Ian Campbell wrote:
> > > Could we enable CONFIG_PSTORE for arm64 as well, please?
> >
> > Is PSTORE (going to be) a thing on arm64? (I'm not entirely sure what
> > pstore is, so sorry if this is a silly question).
>
> I am actually not concerned about pstore itself, but rather by the
> lack of similarity between platforms.
Consistency is a worthwhile goal, but not at the expense of enabling
legacy x86 junk on new architectures where it can never have any
relevance. I don't know if pstore fits that bill, which is why I was
asking about it.
If pstore is going to be a useful thing on arm64 then of course we
should enable it. We should *not* enable it purely to gain the side
effect of loading efivars (the more so since as discussed below it seems
like efivars itself is a legacy interface).
> > Is efivars needed only for efibootmgr or are there other reasons to want
> > it?
>
> The /sys/firmware/efi/vars interface exported by efivars is actually a
> legacy api (efivarfs is the preferred one), but since it is still
> shipped, alignment across architectures would be desirable.
Enabling legacy stuff on new architectures by default is not inherently
desirable IMHO. It would be far better to use the new/proper stuff right
out the gate, at least by default.
> There may or may not currently be other users than efibootmgr.
I can see references in the efivars package (which provides libefivars,
which efibootmgr uses) to efivarfs. Which suggests to me that loading
efivars is not what is needed, but rather the automounting
of /sys/firmware/efi/vars is. That would need to be a bug against some
other package (the mountkernfs.sh providing one would be my best guess,
which may well be systemd these days via some other means, #744301 seems
related, although it goes further).
> > (I don't have an x86 EFI system available to poke around and answer
> > these for myself).
> >
> > I'm wondering if we ought to figure out how to load it automatically
> > independent of the pstore stuff, for all arches.
>
> I'd be happy for it not to be autoloaded, as long as it was consistent
> across architectures.
I think (although I'm somewhat inferring some pieces) that the right
answer here is to have something (mountkernfs.sh/systemd/pixies) mount
efivarfs and to ignore the deprecated efivars thing on non-x86. The
pstore stuff should be considered a separate feature request in its own
right.
I could clone this bug and retitle+reassign the other half into a bug to
handle the efi half, but TBH I think conflating the EFI variable access
from userspace requirement with enabling pstore in the kernel is just
going to end up causing confusion, so a separate report to get efivarfs
mounted would probably be best.
Ian.
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