From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Linux with kvm-intel locks up VMplayer guest is started Date: Wed, 18 Jun 2008 15:59:33 -0500 Message-ID: <48597735.50905@codemonkey.ws> References: <20080616150550.GA16086@deprecation.cyrius.com> <48568503.90607@codemonkey.ws> <20080617123918.GA2397@deprecation.cyrius.com> <4857B92F.9020309@codemonkey.ws> <20080617133234.GE2397@deprecation.cyrius.com> <4857FDE3.8050602@codemonkey.ws> <48591412.2060602@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Martin Michlmayr , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: Received: from yw-out-2324.google.com ([74.125.46.29]:25160 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750999AbYFRU74 (ORCPT ); Wed, 18 Jun 2008 16:59:56 -0400 Received: by yw-out-2324.google.com with SMTP id 9so248045ywe.1 for ; Wed, 18 Jun 2008 13:59:55 -0700 (PDT) In-Reply-To: <48591412.2060602@qumranet.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Anthony Liguori wrote: >> >> We know exactly what the problem is. KVM activates VT >> unconditionally. There's no hardware mechanism to arbitrate access >> to VT. KVM is the only thing in the Linux kernel that uses VT so we >> don't have a software mechanism to arbitrate access to VT. >> >> If the VMware code was upstream, then we could work together to make >> a software arbitration mechanism. It's not, and worse yet, it's >> closed source so there's no chance it will be. Even if someone wrote >> an arbitration mechanism and got VMware to use it, it still shouldn't >> be merged because KVM would be the only thing using that mechanism >> upstream. I'm not interested in adding kernel infrastructure to >> support external binary kernel modules. > > Well a recent patch from Eli Collins mentioned VMware are > standardizing CR4.VMXE as an indicator of whether someone is using the > VT hardware or not, and now kvm clears that bit when unloading. We > could check the bit and fail if is set, thus have working mutual > exclusion. Of course, it will only work with newer versions of kvm > and vmware. Yup, but the original bug reporter would not be helped by this. > I don't see any reason to poke sticks into the wheels here. An occasional poke at binary kernel modules is always a good thing IMHO :-) Regards, Anthony Liguori