[Qemu-devel] Re: [SeaBIOS] seabios: acpi: add _RMV control method for PCI devices

[Avi Kivity <avi@redhat.com>]

On 12/13/2010 10:49 AM, Gleb Natapov wrote:
> On Mon, Dec 13, 2010 at 10:41:25AM +0200, Avi Kivity wrote:
> >  On 12/13/2010 02:00 AM, Marcelo Tosatti wrote:
> >  >On Sat, Dec 11, 2010 at 09:39:30AM +0200, Avi Kivity wrote:
> >  >>   On 12/08/2010 07:08 PM, Marcelo Tosatti wrote:
> >  >>   >Use _RMV method to indicate whether device can be removed.
> >  >>   >
> >  >>   >Data is retrieved from QEMU via I/O port 0xae0c.
> >  >>   >
> >  >>
> >  >>   Where did this port come from?
> >  >
> >  >Its the next available address after "PCI EJ base", used
> >  >for QEMU<->ACPI hotplug communication.
> >  >
> >  >>   What's the protocol?
> >  >
> >  >ACPI reads the 32-bit field indicating the return value of the _RMV
> >  >method (which is used by Windows to decide removability). 1-bit per
> >  >slot.
> >  >
> >  >More ports have to be registered if more buses are added.
> >  >
> >  >>   Maybe we should do this via fw_cfg.
> >  >
> >  >I don't see a need for it? (yes, it might be possible, but i'm not
> >  >familiar enough with AML).
> >
> >  To avoid adding tons of undocumented I/O ports, and to allow
> >  discoverability (what happens with a new seabios on old qemu)?
> >
> We already have out own mini pci hot-plug controller at io port 0xae00.
> The patch just extends its functionality a bit. Logically this
> functionality belongs there.

Well, at least it should be documented.

We could also deprecate the old port and use fwcfg for everything (try 
fwcfg, fall back to ae00).

> >  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.

-- 
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