On Mon, Nov 19, 2018 at 12:56:56PM -0500, Sinan Kaya wrote:

On 11/19/2018 12:41 PM, Keith Busch wrote:

quoted

quoted

Still, breaking existing systems that rely on HEST table is not cool.
I'd rather have users specify "pcie_ports=native" to skip FF rather than
having broken systems by default to be honest.

The pcie_ports=native work-around ignores FF to potentially unknown
results, though.

How about being able to enable/disable FF in BIOS?

We can't really turn off firmware first in the kernel without asking help
from the firmware.

The _OSC method this patch utilizes is the ACPI spec defined way for
the kernel to wrest control from firmware. BIOS specific menu settings
shouldn't be our only recourse when we have a spec authority defining
generic OS interfaces to accomplish the same thing.

Unless there is a disagreement on the _OSC interpreation, we'd have to
accept that platforms breaking from this patch are non-compliant.

Like you said, it causes unpredictable results.

There will be two competing software trying to touch the same registers.