From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=55975 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PnTd1-0007za-CL for qemu-devel@nongnu.org; Thu, 10 Feb 2011 05:20:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PnTcu-0002wc-Tt for qemu-devel@nongnu.org; Thu, 10 Feb 2011 05:19:54 -0500 Received: from mail-fx0-f45.google.com ([209.85.161.45]:46417) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PnTcu-0002wH-JI for qemu-devel@nongnu.org; Thu, 10 Feb 2011 05:19:52 -0500 Received: by fxm12 with SMTP id 12so1314664fxm.4 for ; Thu, 10 Feb 2011 02:19:51 -0800 (PST) Message-ID: <4D53BBC4.8030309@codemonkey.ws> Date: Thu, 10 Feb 2011 11:19:48 +0100 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] KVM call minutes for Feb 8 References: <4D526D0D.9020507@codemonkey.ws> <4D52A86A.1030407@codemonkey.ws> <4D52F20A.7070009@codemonkey.ws> <4D539800.3070802@codemonkey.ws> <20110210090748.GD673@redhat.com> <4D53B752.1080804@codemonkey.ws> <20110210101004.GA20307@redhat.com> In-Reply-To: <20110210101004.GA20307@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Blue Swirl , Chris Wright , Markus Armbruster , kvm@vger.kernel.org, qemu-devel@nongnu.org On 02/10/2011 11:10 AM, Gleb Natapov wrote: > On Thu, Feb 10, 2011 at 11:00:50AM +0100, Anthony Liguori wrote: > >> On 02/10/2011 10:07 AM, Gleb Natapov wrote: >> >>> So what if it is easier, it doesn't mean it is correct thing to do. >>> >> If we spend the next 10 years trying to do the "correct thing" for >> some arbitrary definition of correct, that's not terribly useful. >> > Changing direction by 180 every 2 years even less useful. > If we think through what we are doing and have a coherent architecture before changing direction, then we won't have this problem. >> It's really simple actually. Let's do the least clever thing and >> model how hardware actual works. Once we have that, we can try to >> be better than real hardware (if it's possible). >> > I think out understanding on how HW actually works is very different. > You are placing to much value on were device resides physically, for me > it is completely unimportant detail. Not worth even mentioning. > No, I place value on how things are modelled in the real world. There simply aren't PC's out there that lack an RTC so I have no interest in jumping through hoops in QEMU to make it possible to do this without modifying QEMU code. It might sound nice to a developer but it's of absolutely no use to users. >>>> If all composition is done through a factory interface, it doesn't. >>>> But my main argument here is that we shouldn't try to make all >>>> composition done through a factory interface--only where it makes >>>> sense. >>>> >>>> So very concretely, I'm suggesting we do the following to target-i386: >>>> >>>> 1) make the i440fx device have an embedded ide controller, piix3, >>>> and usb controller that get initialized automatically. The piix3 >>>> embeds the PCI-to-ISA bridge along with all of the default ISA >>>> devices (rtc, serial, etc.). >>>> >>> This may be a problem even from security point of view. What if usb code >>> (ide, serial, parallel) has guest exploitable bug? Currently I can happily >>> continue running guests if they do not need affected subsystem. If we'll >>> get it your way I will no longer be able to do so. >>> >> qemu -device i440fx,ide=off >> >> > So you still need to support arbitrary composition. What's the > difference? No, we don't. It's possible to have an 'rtc=off' option but I'm tremendously opposed to doing this. Arbitrary composition is not a useful goal IMHO. > So why do you like -device i440fx over what we have now? > Because I don't think tools like libvirt should be doing device composition to create an i440fx-like chipset. I think the current path we're on is pushing too much logic that belongs in QEMU into the management stack. > In current speak you propose will be implement by using i440fx machine > type. Qdev will build it for you. > If you had an i440fx machine type, that had no non-optional components added, and you could specify options to the machine type, yes. But I think you'll agree that there's no reason to not just treat the i440fx as a device. >> If you really care to do this. But this desire to remove devices is >> silly IMHO. Concerns about security are misplaced. If you have to >> change the way a guest is invoked in order to eliminate security >> problems, then there's something seriously wrong. >> >> > No I do not. I do not create guest with unneeded devices from the > beginning. > There is very little that isn't 'unneeded'. Regards, Anthony Liguori > -- > Gleb. >