From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC PATCH 00/18] KVM: x86: CPU isolation and direct interrupts handling by guests Date: Thu, 28 Jun 2012 20:34:52 +0300 Message-ID: <4FEC95BC.200@redhat.com> References: <20120628060719.19298.43879.stgit@localhost.localdomain> <4FEC8D31.3070406@redhat.com> <4FEC93BD.2070809@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Tomoki Sekiyama , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, yrl.pp-manager.tt@hitachi.com To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48674 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753951Ab2F1Re6 (ORCPT ); Thu, 28 Jun 2012 13:34:58 -0400 In-Reply-To: <4FEC93BD.2070809@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/28/2012 08:26 PM, Jan Kiszka wrote: >> >> This is both impressive and scary. What is the target scenario here? >> Partitioning? I don't see this working for generic consolidation. >> > > From my POV, partitioning - including hard realtime partitions - would > provide some use cases. But, as far as I saw, there are still major > restrictions in this approach, e.g. that you can't return to userspace > on the slave core. Or even execute the in-kernel device models on that core. > > I think we need something based on the no-hz work on the long run, ie. > the ability to run a single VCPU thread of the userland hypervisor on a > single core with zero rescheduling and unrelated interruptions - as far > as the guest load scenario allows this (we have some here). What we can do perhaps is switch from direct mode to indirect mode on exit. Instead of running with interrupts disabled, enable interrupts and make sure they are forwarded to the guest on the next entry. > Well, and we need proper hardware support for direct IRQ injection on x86... Hardware support always helps, but it always seems to come after the software support is in place and needs to be supported forever. -- error compiling committee.c: too many arguments to function