On Wed, Nov 14, 2018 at 07:22:04PM +0000, Alex_Gagniuc@Dellteam.com wrote:

On 11/14/2018 12:00 AM, Bjorn Helgaas wrote:

quoted

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?

quoted

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?