From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:56903) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TaaAJ-0007at-4n for qemu-devel@nongnu.org; Mon, 19 Nov 2012 17:50:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TaaAF-0001j5-Fr for qemu-devel@nongnu.org; Mon, 19 Nov 2012 17:50:07 -0500 Date: Tue, 20 Nov 2012 09:51:43 +1100 From: David Gibson Message-ID: <20121119225143.GD18362@truffula.fritz.box> References: <1352774820-22804-1-git-send-email-david@gibson.dropbear.id.au> <1352774820-22804-13-git-send-email-david@gibson.dropbear.id.au> <7D986011-0512-4492-92AE-F8A331C9FB4A@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7D986011-0512-4492-92AE-F8A331C9FB4A@suse.de> Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: "qemu-ppc@nongnu.org List" , qemu-devel qemu-devel , "Michael S. Tsirkin" On Mon, Nov 19, 2012 at 05:34:12PM +0100, Alexander Graf wrote: > > On 13.11.2012, at 03:47, David Gibson wrote: > > > From: Alexey Kardashevskiy > > > > In future (with VFIO) we will have multiple PCI host bridges on > > pseries. Each one needs a unique LIOBN (IOMMU id). At the moment we > > derive these from the pci domain number, but the whole notion of > > domain numbers on the qemu side is bogus and in any case they're not > > actually uniquely allocated at this point. > > > > This patch, therefore uses a simple sequence counter to generate > > unique LIOBNs for PCI host bridges. > > > > Signed-off-by: Alexey Kardashevskiy > > Signed-off-by: David Gibson > > I don't really like the idea of having a global variable just > because our domain ID generation seems to not work as > expected. Michael, any comments here? Well, the patch I sent which changed domain id generation was ignored. In any case, as I said, the whole concept of domain numbers makes no sense on the qemu side, so I don't think increasing reliance on them by using them here is a good idea. It would be conceptually nicer to derive the liobn from the buid, but that would rely on the buid's being unique in the low 32-bits, which is true in practice, but seems risky to rely on. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson