From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: Use thread debug register storage instead of kvm specific data Date: Tue, 01 Sep 2009 14:34:12 +0300 Message-ID: <4A9D06B4.4060708@redhat.com> References: <1251798248-13164-1-git-send-email-avi@redhat.com> <20090901112220.GA18271@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Jan Kiszka To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49607 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754022AbZIALeO (ORCPT ); Tue, 1 Sep 2009 07:34:14 -0400 In-Reply-To: <20090901112220.GA18271@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 09/01/2009 02:22 PM, Marcelo Tosatti wrote: > On Tue, Sep 01, 2009 at 12:44:08PM +0300, Avi Kivity wrote: > >> Instead of saving the debug registers from the processor to a kvm data >> structure, rely in the debug registers stored in the thread structure. >> This allows us not to save dr6 and dr7. >> >> Reduces lightweight vmexit cost by 350 cycles, or 11 percent. >> > Is this kgdb safe? > I don't think so - kgdb seems to access the debug registers directly. I think we can live with it at the moment, and later add an API to arbitrate debug register usage among the various users (kgdb seems to be unsafe wrt userspace debug as well). -- error compiling committee.c: too many arguments to function