From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:45592) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ry8LS-0000Bb-KT for qemu-devel@nongnu.org; Thu, 16 Feb 2012 15:54:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ry8LR-0003w4-G7 for qemu-devel@nongnu.org; Thu, 16 Feb 2012 15:54:26 -0500 Received: from relay1.mentorg.com ([192.94.38.131]:55899) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ry8LR-0003tF-Bk for qemu-devel@nongnu.org; Thu, 16 Feb 2012 15:54:25 -0500 From: Paul Brook Date: Thu, 16 Feb 2012 20:54:17 +0000 References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201202162054.18209.paul@codesourcery.com> Subject: Re: [Qemu-devel] VirtIO 9p mount_tag (bogus?) limit of 32 bytes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: C Anthony Risinger > i see an error message has been added, which is great (i killed a > couple hours of $%!@ until i noticed the truncated length was *exactly > 32* bytes; silent truncation), but it would really be great if this > restriction could be lifted, or at least mitigated by expanding the > field some. > > is config space that precious? Yes. > what constrains it (personal curiosity :-)? Virtio PCI devices map the config space directly onto an ISA IO port range, along with the virtio control structure. On most systems (in particular anything PC based) this is a 16-bit address space. i.e. you have substantually less than 64k of virtio config space for the whole machine, and potentially only a couple of kbytes for a given PCI bus. Paul