[+cc Keith, Sinan, Tyler] On Wed, Apr 29, 2020 at 03:24:41PM +0000, Austin.Bolen@xxxxxxxx wrote: > On 4/28/2020 3:37 PM, Bjorn Helgaas wrote: > > [+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. > > [2] https://lkml.org/lkml/2018/11/16/202 Wow, egg on my face :( How embarrassing. Alex posted the *identical* patch 18 months ago. There was a lot of discussion the first time, but I certainly should have applied this the second time around when that had been resolved. Anyway, I did apply it now on pci/error for v5.8, and I added links to Alex's posting as well as his sign-off, since he actually did all the work earlier. I apologize for missing this. This still leaves patch [2/2] from Alex and the second half of Sathy's patch. They're similar but not identical, so I'll try to sort that out next. > > 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 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 > > > >> commit 8f8e42e7c2dd ("PCI/AER: Use only _OSC to determine AER ownership") > >> Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > >> Date: Mon Apr 27 18:25:13 2020 -0500 > >> > >> PCI/AER: Use only _OSC to determine AER ownership > >> > >> Per the PCI Firmware spec, r3.2, sec 4.5.1, the OS can request control of > >> AER via bit 3 of the _OSC Control Field. In the returned value of the > >> Control Field: > >> > >> The firmware sets [bit 3] to 1 to grant control over PCI Express Advanced > >> Error Reporting. ... after control is transferred to the operating > >> system, firmware must not modify the Advanced Error Reporting Capability. > >> If control of this feature was requested and denied or was not requested, > >> firmware returns this bit set to 0. > >> > >> Previously the pci_root driver looked at the HEST FIRMWARE_FIRST bit to > >> determine whether to request ownership of the AER Capability. This was > >> based on ACPI spec v6.3, sec 18.3.2.4, and similar sections, which say > >> things like: > >> > >> Bit [0] - FIRMWARE_FIRST: If set, indicates 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. > >> > >> These ACPI references don't say anything about ownership of the AER > >> Capability. > >> > >> Remove use of the FIRMWARE_FIRST bit and rely only on the _OSC bit to > >> determine whether we have control of the AER Capability. > >> > >> Link: https://lore.kernel.org/r/67af2931705bed9a588b5a39d369cb70b9942190.1587925636.git.sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx > >> [bhelgaas: commit log, split patches] > >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > >> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > >> > >> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c > >> index ac8ad6cb82aa..9e235c1a75ff 100644 > >> --- a/drivers/acpi/pci_root.c > >> +++ b/drivers/acpi/pci_root.c > >> @@ -483,13 +483,8 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm, > >> if (IS_ENABLED(CONFIG_HOTPLUG_PCI_SHPC)) > >> control |= OSC_PCI_SHPC_NATIVE_HP_CONTROL; > >> > >> - if (pci_aer_available()) { > >> - if (aer_acpi_firmware_first()) > >> - dev_info(&device->dev, > >> - "PCIe AER handled by firmware\n"); > >> - else > >> - control |= OSC_PCI_EXPRESS_AER_CONTROL; > >> - } > >> + if (pci_aer_available()) > >> + control |= OSC_PCI_EXPRESS_AER_CONTROL; > >> > >> /* > >> * Per the Downstream Port Containment Related Enhancements ECN to > >> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c > >> index f4274d301235..efc26773cc6d 100644 > >> --- a/drivers/pci/pcie/aer.c > >> +++ b/drivers/pci/pcie/aer.c > >> @@ -318,30 +318,6 @@ int pcie_aer_get_firmware_first(struct pci_dev *dev) > >> aer_set_firmware_first(dev); > >> return dev->__aer_firmware_first; > >> } > >> - > >> -static bool aer_firmware_first; > >> - > >> -/** > >> - * aer_acpi_firmware_first - Check if APEI should control AER. > >> - */ > >> -bool aer_acpi_firmware_first(void) > >> -{ > >> - static bool parsed = false; > >> - struct aer_hest_parse_info info = { > >> - .pci_dev = NULL, /* Check all PCIe devices */ > >> - .firmware_first = 0, > >> - }; > >> - > >> - if (pcie_ports_native) > >> - return false; > >> - > >> - if (!parsed) { > >> - apei_hest_parse(aer_hest_parse, &info); > >> - aer_firmware_first = info.firmware_first; > >> - parsed = true; > >> - } > >> - return aer_firmware_first; > >> -} > >> #endif > >> > >> #define PCI_EXP_AER_FLAGS (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \ > >> @@ -1523,7 +1499,7 @@ static struct pcie_port_service_driver aerdriver = { > >> */ > >> int __init pcie_aer_init(void) > >> { > >> - if (!pci_aer_available() || aer_acpi_firmware_first()) > >> + if (!pci_aer_available()) > >> return -ENXIO; > >> return pcie_port_service_register(&aerdriver); > >> } > >> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h > >> index 2d155bfb8fbf..11c98875538a 100644 > >> --- a/include/linux/pci-acpi.h > >> +++ b/include/linux/pci-acpi.h > >> @@ -125,10 +125,4 @@ static inline void acpi_pci_add_bus(struct pci_bus *bus) { } > >> static inline void acpi_pci_remove_bus(struct pci_bus *bus) { } > >> #endif /* CONFIG_ACPI */ > >> > >> -#ifdef CONFIG_ACPI_APEI > >> -extern bool aer_acpi_firmware_first(void); > >> -#else > >> -static inline bool aer_acpi_firmware_first(void) { return false; } > >> -#endif > >> - > >> #endif /* _PCI_ACPI_H_ */ > >
