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From:   <Alex_Gagniuc@Dellteam.com>
To:     <okaya@kernel.org>, <mr.nuke.me@gmail.com>, <keith.busch@intel.com>
Subject: Re: [PATCH 0/2] PCI/AER: Consistently use _OSC to determine who owns
 AER
Thread-Topic: [PATCH 0/2] PCI/AER: Consistently use _OSC to determine who owns
 AER
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Date:   Tue, 20 Nov 2018 21:46:13 +0000
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On 11/20/2018 03:02 PM, Sinan Kaya wrote:=0A=
> On 11/20/2018 3:44 PM, Alex_Gagniuc@Dellteam.com wrote:=0A=
>> I'd prefer "sure" instead of "think". "I think it breaks some system I'm=
=0A=
>> not telling you about" doesn't help much in figuring out how not to=0A=
>> break said system(s).:)=0A=
> =0A=
> Sorry, I thought I mentioned why it would break but let me repeat.=0A=
=0A=
Why, yes, but bets are still being placed on the systems allegedly =0A=
suffering from this.=0A=
=0A=
=0A=
> The systems I have seen rely on the HEST table presence as an indicator=
=0A=
> to the OS that firmware first is enabled. If you go look at the _OSC bits=
=0A=
> on such systems, it still says OS owns the AER service.=0A=
> =0A=
> The assumption here is that HEST table has precedence over the _OSC bits.=
=0A=
> That's what needs to be clarified in the UEFI forum.=0A=
> =0A=
> If this code is to go in and ignore the HEST table presence, then firmwar=
e=0A=
> will think that it owns AER service and OS will think that it owns AER=0A=
> service too.=0A=
=0A=
So this seems like exactly the scenario we were hypothesizing.=0A=
=0A=
  * System boots up with FFS enabled. Everything is fine so far.=0A=
  * OSPM requests control of AER (set bit 3 in _OSC)=0A=
  * FW grants OS control of AER (set bit 3 in _OSC reply)=0A=
=0A=
That's how things are designed to work.=0A=
=0A=
=0A=
Now, let's assume, for the sake of argument, that the firmware on those =0A=
system's is broken, and it didn't intend to give the OS control of AER. =0A=
OSPM checking HEST instead of _OSC is still wrong, according to the =0A=
spec. Two wrongs don't make a right, they just don't crash.=0A=
=0A=
I think the correct way is to identify those broken systems, and add =0A=
quirks for them. Continuing to have inconsistent and over-complicated =0A=
logic that is not spec compliant is not any better.=0A=
=0A=
Alex=0A=