From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58991) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UmJOD-00054z-J7 for qemu-devel@nongnu.org; Tue, 11 Jun 2013 03:53:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UmJOA-0008Ts-Mx for qemu-devel@nongnu.org; Tue, 11 Jun 2013 03:53:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59780) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UmJOA-0008St-DY for qemu-devel@nongnu.org; Tue, 11 Jun 2013 03:53:10 -0400 Date: Tue, 11 Jun 2013 10:53:14 +0300 From: "Michael S. Tsirkin" Message-ID: <20130611075314.GG31474@redhat.com> References: <1370882347-31129-1-git-send-email-mst@redhat.com> <51B6B68E.9040508@redhat.com> <20130611065525.GB31474@redhat.com> <51B6D4E5.2070100@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51B6D4E5.2070100@redhat.com> Subject: Re: [Qemu-devel] [PATCH] qemu: piix: PCI bridge ACPI hotplug support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: Peter Maydell , Anthony Liguori , David Woodhouse , seabios@seabios.org, qemu-devel@nongnu.org, Kevin O'Connor , Jordan Justen , Laszlo Ersek On Tue, Jun 11, 2013 at 09:42:29AM +0200, Gerd Hoffmann wrote: > Hi, > > >>> Portability: > >>> - Non x86 (or any Linux) platforms don't need any of this code. > >>> They can keep happily using SHPC the way > >>> they always did. > >> > >> Hmm. Is is possible to write a SHPC driver in AML? I think it would be > >> alot better to have one guest/host interface for pci bridge hotplug > >> instead of two. > >> > >> cheers, > >> Gerd > > > > No, it's not possible, SHPC is not designed to be used from ACPI. > > > > Two reasons off the top of my head, there are likely others: > > > > 1. SHPC uses regular PCI interrupts to signal events. It does not signal > > GFE and SCI. > > > > 2. SHPC uses config accesses to get information from device. > > ACPI does not allow config access anywhere except the root bus from ACPI > > (This requirement is designed to give the OS freedom > > to reconfigure PCI in an arbitrary way). > > OK, so it's designed for OSes to have native SHPC support. Linux has that? Yes. > Quick googling found me Windows Vista+ has it too, correct? So that > leaves Win2k + WinXP versions. Older Windows versions do not support > pci hotplug at all. Win2k is EOL already. WinXP will follow soon. > > More users? googling lead you astray. No windows version supports SHPC. > /me wonders whenever it is worth hopping through the loops needed to > support ACPI-based hotplug of devices behind bridges in the first place. > > cheers, > Gerd Yes and not just because of windows guests. ACPI spec is also very explicit that native hotplug is an optional feature. Test suites such as WHQL are known to test spec compliance. -- MST