Re: [Qemu-devel] [PATCH] seabios: acpi: Add _STA for PCI hotplug slots

[Kevin O'Connor]

On Fri, Feb 24, 2012 at 04:21:17PM -0700, Alex Williamson wrote:
> When a Status method is provided on a slot, the OSPM evaluates
> _STA in response to the device check notify on the slot.  This
> allows some degree of a handshake between the platform and the
> OSPM that the hotplug has been acknowledged.
> 
> In order to implement _STA, we need to know which slots have
> devices.  A slot with device returns 0x0F, a slot without a
> device returns Zero.  We get this information from Qemu using
> the 0xae08 I/O port register.  This was previously the read-side
> of the register written to commit a device eject and always
> returned 0 on read.  It now returns a bitmap of present slots,
> so we know that reading 0 means we have and old Qemu and
> dynamically modify our SSDT to rename the _STA methods.  This
> is necessary to allow backwards compatibility.
> 
> The _STA method also writes the slot identifier to I/O port
> register 0xae00 as an acknowledgment of the hotplug request.

Thanks.  The patch looks fine to me.  However, since I'm not all that
familiar with the details of the qemu/kvm support for this, I'd like
to see an Ack from one of the qemu or kvm maintainers.

-Kevin