On Mon, Dec 13, 2010 at 11:10:38AM +0200, Avi Kivity wrote:
On 12/13/2010 11:03 AM, Gleb Natapov wrote:
We could also deprecate the old port and use fwcfg for everything (try fwcfg, fall back to ae00).
fwcfg designed to be simple for easy use by firmware. It has two port one for index another for value, so its use is racy in multi-threaded SMP environment. DSDT code is executed in such environment. There is lock facility in AML, but why complicate things.
I prefer to remove complexity from interfaces and have it in the implementation instead.
I prefer whatever is simpler :) simpler == less bugs. And it is not like we discuss new interface here. You want to deprecate existing interface in favor of something that was not designed to handle the task.
We could do this in two ways: by adding a fwcfg client to the DSDT, or by copying the information to system memory, and referencing system memory from the DSDT.
This is even worse. It requires some fixed address to be shared between DSDT and Seabios (or alternatively Seabios will have to generate this part of DSDT dynamically).
Could easily be something in the F segment.
Yes, but then we will have two magic values (fwcfg index + address in F segment) instead of one (address of pci hot-plug controller).
The F segment address is internal to SeaBIOS; it isn't an external interface.
Depends on how you define external interface. It can be considered as interface between OSPM and firmware. Next time layout of F segment changes in SeaBIOS will you remember fixing DSDT too?
-- Gleb.