On Wed, Apr 29, 2020 at 03:24:41PM +0000, Austin.Bolen@xxxxxxxx wrote: > On 4/28/2020 3:37 PM, Bjorn Helgaas wrote: > > [EXTERNAL EMAIL] > > > > [+to Mario, Austin, Rafael; Dell folks, I suspect this commit will > > break Dell servers but I'd like your opinion] > > > > <snip> > Thanks Bjorn, for the heads up. I checked with our server BIOS team and > they say that only checking _OSC for AER should work on our servers. We > always configure_OSC and the HEST FIRMWARE_FIRST flag to retain firmware > control of AER so either could be checked. > > > I *really* want the patch because the current mix of using both _OSC > > and FIRMWARE_FIRST to determine AER capability ownership is a mess and > > getting worse, but I'm more and more doubtful. > > > > My contention is that if firmware doesn't want the OS to use the AER > > capability it should simply decline to grant control via _OSC. > > I agree per spec that _OSC should be used and this was confirmed by the > ACPI working group. Alex had submitted a patch for us [2] to switch to > using _OSC to determine AER ownership following the decision in the ACPI > working group. Perfect, thank you! I had forgotten that Alex posted that. We should add credit to him and a link to that discussion. Thanks again! > [2] https://lkml.org/lkml/2018/11/16/202 > > > But things like 0584396157ad ("PCI: PCIe AER: honor ACPI HEST FIRMWARE > > FIRST mode") [1] suggest that some machines grant AER control to the > > OS via _OSC, but still expect the OS to leave AER alone for certain > > devices. > > AFAIK, no Dell server, including the 11G servers mentioned in that > patch, have granted control of AER via _OSC and set HEST FIRMWARE_FIRST > for some devices. I don't think this model is even support by the > ACPI/PCIe standards. Yes, you can set the bits that way, but there is > no text I've found that says how the OS/firmware should behave in that > scenario. In order to be interoperable, I think someone would need to > standardized how the OS/firmware would could co-ordinate in such a model. I agree and I want to get Linux out of the current muddle where we try to make sense out of it. > > I think the FIRMWARE_FIRST language in the ACPI spec is really too > > vague to tell the OS not to use the AER Capability, but it seems like > > that's what commits like [1] rely on. > > > > The current _OSC definition (PCI Firmware r3.2) applies only to > > PNP0A03/PNP0A08 devices, but it's conceivable that it could be > > extended to other devices if we need per-device AER Capability > > ownership. > > > > [1] https://git.kernel.org/linus/0584396157ad <snip>
