From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33821) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XddHl-0003jL-Ds for qemu-devel@nongnu.org; Mon, 13 Oct 2014 06:55:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XddHa-0004bi-Vs for qemu-devel@nongnu.org; Mon, 13 Oct 2014 06:55:29 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:33761) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XddHa-0004aw-N2 for qemu-devel@nongnu.org; Mon, 13 Oct 2014 06:55:18 -0400 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 13 Oct 2014 11:55:16 +0100 Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 58D8617D8056 for ; Mon, 13 Oct 2014 11:57:29 +0100 (BST) Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s9DAtDCE54001742 for ; Mon, 13 Oct 2014 10:55:13 GMT Received: from d06av05.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s9DAtDSH030181 for ; Mon, 13 Oct 2014 04:55:13 -0600 Date: Mon, 13 Oct 2014 12:55:11 +0200 From: Cornelia Huck Message-ID: <20141013125511.5d3475ab.cornelia.huck@de.ibm.com> In-Reply-To: <87bnpgecqx.fsf@rustcorp.com.au> References: <1412692807-12398-1-git-send-email-cornelia.huck@de.ibm.com> <1412692807-12398-4-git-send-email-cornelia.huck@de.ibm.com> <87bnpgecqx.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC 03/11] virtio: support more feature bits List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Rusty Russell Cc: thuth@linux.vnet.ibm.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org On Mon, 13 Oct 2014 16:23:58 +1030 Rusty Russell wrote: > Cornelia Huck writes: > > With virtio-1, we support more than 32 feature bits. Let's make > > vdev->guest_features depend on the number of supported feature bits, > > allowing us to grow the feature bits automatically. > > It's a judgement call, but I would say that simply using uint64_t > will be sufficient for quite a while. I prefer this as an array for two reasons: - It matches what ccw does anyway (we read/write features in chunks of 32 bit), so this makes the backend handling for this transport very straightforward. - While I don't see us running out of 64 feature bits for a while, we'd have to touch every device and transport again when we do. I'd prefer to do this once, as we need to change code anyway.