From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v3 1/3] Introduce a workqueue to deliver PIT timer interrupts. Date: Tue, 17 Apr 2012 18:15:05 +0200 Message-ID: <4F8D9709.3020409@siemens.com> References: <1276722673-19011-2-git-send-email-clalance@redhat.com> <4F8C49D6.9010603@siemens.com> <20120417093123.GB11918@redhat.com> <4F8D44B8.1000102@redhat.com> <20120417102601.GF11918@redhat.com> <4F8D45F0.4020908@redhat.com> <20120417103106.GG11918@redhat.com> <4F8D4917.5000703@redhat.com> <20120417110506.GJ11918@redhat.com> <4F8D5B4A.6070904@redhat.com> <20120417120340.GL11918@redhat.com> <4F8D5CBD.1070004@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , "kvm@vger.kernel.org" , Marcelo Tosatti To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:21551 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755863Ab2DQQPJ (ORCPT ); Tue, 17 Apr 2012 12:15:09 -0400 In-Reply-To: <4F8D5CBD.1070004@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-04-17 14:06, Avi Kivity wrote: > On 04/17/2012 03:03 PM, Gleb Natapov wrote: >>> >>> KVM_MAX_VCPUS. >>> >> Ah, so you are worried about malicious guest configuring pit to >> broadcast to all its vcpus. > > Yes - it can introduce huge amounts of latency this way which is exactly > what Jan is trying to prevent. > > Though I'm not sure spin_lock_irq() in the realtime tree actually > disables irqs (but it's certainly not a good idea in mainline; it's > nasty even with just the spinlock). This depends on how you declare the spin lock type - raw or normal. The former will disable irqs, the latter not even preemption (but become a mutex). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux