From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH 1/2] KVM: Convert kvm_lock to raw_spinlock Date: Wed, 09 Feb 2011 13:31:01 +0100 Message-ID: <4D528905.8030802@siemens.com> References: <4D512F35.1050108@siemens.com> <4D525D30.2000402@redhat.com> <4D525D7D.8080306@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , Zachary Amsden To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:17961 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754706Ab1BIMbP (ORCPT ); Wed, 9 Feb 2011 07:31:15 -0500 In-Reply-To: <4D525D7D.8080306@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2011-02-09 10:25, Avi Kivity wrote: > On 02/09/2011 11:24 AM, Avi Kivity wrote: >> On 02/08/2011 01:55 PM, Jan Kiszka wrote: >>> Code under this lock requires non-preemptibility. Ensure this also over >>> -rt by converting it to raw spinlock. >>> >> >> Please add a code comment documenting what data under this lock >> requires it to be a raw spinlock. >> > > Or better, put it in Documentation/kvm/locking.txt, which we'll try to > grow to cover all locks. > Something like [Documentation/kvm/locking.txt] KVM Lock Overview ----------------- 1. Spin locks 1.1 tsc_write_lock Type: raw Arch: x86 Protects: kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset} tsc offset in vmcb Comment: 'raw' because updating the tsc offsets must not be preempted ... ? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux