Re: [RFC/RFT PATCH 0/2] disable_hest quirk on HP m400 with bad UEFI firmwware

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Thu, Jun 28, 2018 at 12:25:06PM +0200, Ard Biesheuvel wrote:
> Hi James,
> 
> On 28 June 2018 at 12:06, James Morse <james.morse@arm.com> wrote:
> > There are reports[0] that HPE's 'ProLiant m400 Server' (aka moonshot) has
> > broken RAS support, and adding disable_hest to the kernel cmdline is the
> > only way to make the board boot if APEI support is built into the kernel.
> >
> > After Mark Salter's investigation[1] we know that UEFI's ExitBootServices
> > is doing something that causes a fatal error to be written to GHES.2.
> > Once the kernel finds this, it falsely assume it was due to something that
> > happened during boot, and panic()s.
> >
> > This series adds a DMI quirks table to hest.c, and adds a helper that lets
> > us query the UEFI system table version, to set hest_disabled on this
> > platform.
> >
> > Testing the HEST table vendor and revision is a problem as this would
> > match all 'HPE ProLiant', some of which may be a totally different CPU
> > architecture.
> >
> >
> > I don't have access to an m400, these DMI and UEFI values were taken from
> > the crashlog report at [0], then tested with the equivalent fields on
> > Seattle.
> >
> 
> I understand the desire to keep running these M400s as long as they
> have some life left in them, but the reality is that they are end of
> life already, and not many were manufactured to begin with.
> 
> Given how the upstream kernel is aimed at future development, I don't
> think we should fix this in the upstream kernel at all. Distros are
> free to do what they like, of course, and I'm sure RedHat already have
> a fix for this in their downstream kernel. But putting this upstream
> means we will never be able to remove it again, which would be
> especially unfortunate given that it is the first ever DMI quirk for
> arm64, which we tried *very* hard to avoid, also because we don't
> initialize the DMI framework as early as x86 does, and so once we open
> the floodgates, we will run into issues where we will need to reorder
> the init sequence to make DMI data available early enough.
> 
> As for the efi.h patch: I don't object to adding code that makes the
> spec revision available, but note that this is *not* a firmware build
> number, and so it should not be used as such. Also, given that m400 is
> EOL and unmaintained, no firmware updates are expected, and so
> assuming that there will be a UEFI 2.7 based update in the future
> seems rather optimistic.
> 
> Ultimately, it is not up to me to decide whether
> 
> a) DMI quirks will be permitted on arm64
> b) we care about m400 enough to put this quirk in the upstream kernel
> 
> but I'd prefer it if we steered clear of this.

I apologise to James (and Mark) who went all the way to debug this FW
bug and worked around it with a series that is upstreamable, I was in
two minds about this but eventually I would agree with you, your
reasoning is linear and it is an acceptable reason not to merge this
series, if HPe do not care I do not think we should either, for the time
being let's keep the floodgates watertight, with my apologies.

Thanks,
Lorenzo