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

[Avi Kivity]

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 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.

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