On Sun, Mar 04, 2012 at 08:30:00PM -0700, Alex Williamson wrote: > On Sun, 2012-03-04 at 20:53 +0200, Michael S. Tsirkin wrote: > > 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. To summarize my previous messages, my notes are - not clear that we want to implement _STA: yes we can tell hypervisor what did _STA report to OSPM but this won't be needed without _STA - assuming we do, it seems clear that we want hypervisor to know what it is that we told OSPM about slot status - the specific interface used for the above is fairly tricky so it needs documentation explaining how both sides cooperate -- MST
