On Wed, Nov 14, 2018 at 07:22:04PM +0000, Alex_Gagniuc@xxxxxxxxxxxx wrote: > On 11/14/2018 12:00 AM, Bjorn Helgaas wrote: > > Just to make sure we're on the same page, can you point me to this > > rule? I do see that OSPM must request control of AER using _OSC > > before it touches the AER registers. What I don't see is the > > connection between firmware-first and the AER registers. > > ACPI 6.2 - 6.2.11.3, Table 6-197: > > PCI Express Advanced Error Reporting control: > * The firmware sets this bit to 1 to grant control over PCI Express > Advanced Error Reporting. If firmware allows the OS control of this > feature, then in the context of the _OSC method it must ensure that > error messages are routed to device interrupts as described in the PCI > Express Base Specification[...] > > Now I'm confused too: > * HEST -> __aer_firmware_first > This is used for touching/not touching AER bits > * _OSC -> bridge->native_aer > Used to enable/not enable AER portdrv service > Maybe Keith knows better why we're doing it this way. From ACPI text, it > doesn't seem that control of AER would be tied to HEST entries, although > in practice, it is. I'm not sure, that predates me. HEST does have a FIRMWARE_FIRST flag, but spec does not say anymore on relation to _OSC control or AER capability. Nothing in PCIe spec either. I also don't know why Linux disables the AER driver if only one device has a FIRMWARE_FIRST HEST. Shouldn't that just be a per-device decision? > > The closest I can find is the "Enabled" field in the HEST PCIe > > AER structures (ACPI v6.2, sec 18.3.2.4, .5, .6), where it says: > > > > If the field value is 1, indicates this error source is > > to be enabled. > > > > If the field value is 0, indicates that the error source > > is not to be enabled. > > > > If FIRMWARE_FIRST is set in the flags field, the Enabled > > field is ignored by the OSPM. > > > > AFAICT, Linux completely ignores the Enabled field in these > > structures. > > I don't think ignoring the field is a problem: > * With FFS, OS should ignore it. > * Without FFS, we have control, and we get to make the decisions anyway. > In the latter case we decide whether to use AER, independent of the crap > in ACPI. I'm not even sure why "Enabled" matters in native AER handling. > Probably one of the check-boxes in "Binary table designer's handbook"? And why doesn't Linux do anything with _OSC response other than logging it? If OS control wasn't granted, shouldn't that take priority over HEST?
