From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:50551) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4RNC-00006F-Sl for qemu-devel@nongnu.org; Mon, 05 Mar 2012 01:26:20 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S4RNB-0008VX-4G for qemu-devel@nongnu.org; Mon, 05 Mar 2012 01:26:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3806) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4RNA-0008VR-T6 for qemu-devel@nongnu.org; Mon, 05 Mar 2012 01:26:17 -0500 Date: Mon, 5 Mar 2012 08:26:23 +0200 From: "Michael S. Tsirkin" Message-ID: <20120305062622.GB22209@redhat.com> References: <20120224231735.17761.31411.stgit@bling.home> <20120304185225.GB16058@redhat.com> <1330918200.29701.214.camel@bling.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1330918200.29701.214.camel@bling.home> Subject: Re: [Qemu-devel] [PATCH] seabios: acpi: Add _STA for PCI hotplug slots List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: seabios@seabios.org, ddutile@redhat.com, qemu-devel@nongnu.org, gleb@redhat.com 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