From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sinan Kaya Subject: Re: [PATCH 0/2] PCI/AER: Consistently use _OSC to determine who owns AER Date: Mon, 19 Nov 2018 15:33:52 -0500 Message-ID: <84013a8a-287d-d700-6710-91cc35f507c8@kernel.org> References: <20181115231605.24352-1-mr.nuke.me@gmail.com> <20181119165318.GB26595@localhost.localdomain> <74f2c527-0890-5e14-5e2d-48934a42dae6@kernel.org> <20181119174127.GE26595@localhost.localdomain> <20181119181051.GA26707@localhost.localdomain> <3f923367-2cc1-c0d6-bca6-bf9a03d1b9ca@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Alex_Gagniuc@Dellteam.com, mr.nuke.me@gmail.com, keith.busch@intel.com Cc: baicar.tyler@gmail.com, Austin.Bolen@dell.com, Shyam.Iyer@dell.com, lukas@wunner.de, bhelgaas@google.com, rjw@rjwysocki.net, lenb@kernel.org, ruscur@russell.cc, sbobroff@linux.ibm.com, oohall@gmail.com, linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org List-Id: linux-acpi@vger.kernel.org On 11/19/2018 3:16 PM, Alex_Gagniuc@Dellteam.com wrote: > On 11/19/2018 01:32 PM, Sinan Kaya wrote: >> ACPI 6.2: >> >> 18.3.2.4 PCI Express Root Port AER Structure >> >> Flags: >> >> Bit [0] - FIRMWARE_FIRST: If set, this bit indicates to the OSPM that system >> firmware will handle errors from this source first. >> Bit [1] - GLOBAL: If set, indicates that the settings contained in this >> structure apply globally to all PCI Express Devices. >> All other bits must be set to zero. >> >> It doesn't say shall, may or might. It says will. > > It says "system firmware will handle errors". It does not say "system > firmware owns AER registers". In absence on any descriptor text on the > meaning of these tables, this really looks to me like it should be > interpreted as a descriptor of APEI error sources, not a mutex on who > writes to certain bits-- AER in this case. True. I was trying to get it out in a rush. I omitted words. However; table assumes governance about for which entities firmware first should be enabled. There is no cross reference to _OSC or permission negotiation like _OST. > > I don't think that is contradictory or inconsistent. > I also wasn't able to find any reference to HEST in UEFI 2.7, only in > ACPI spec. You are right. It was a confusion on my side. The right place to look is ACPI specification. I was involved in this a couple of years ago. Some pieces were in UEFI spec. Other pieces were in ACPI. I guess they got unified now. > >> I think It depends on your PCI topology. >> >> For other topologies with multiple PCI root complexes, I can see this being >> used per root complex flag to indicate which root complex needs firmware first >> and which one doesn't. > > _OSC is per root bus, so it's already granular enough, right? Why would > it depend on PCI topology? > I was speculating. I don't have the full background on this. Need to consult the spec developers. >> As I said in my previous email, the right place to talk about this is UEFI >> forum. > > The way I would present the problem to he spec writers is that, although > the spec appears to be consistent, we've seen firmware vendors that made > the wrong assumptions about HEST/_OSC. Instead of describing AER > ownership with _OSC, they attempted to do it with HEST. So we should add > an implementation note, or clarification about this. I agree. > > Alex >