From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v3) Date: Fri, 03 Dec 2010 17:38:06 -0600 Message-ID: <4CF97F5E.3000704@codemonkey.ws> References: <1291415962-13762-1-git-send-email-aliguori@us.ibm.com> <20101203233231.GA29502@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm@vger.kernel.org, Avi Kivity , Marcelo Tosatti , Chris Wright , Srivatsa Vaddagiri To: Joerg Roedel Return-path: Received: from mail-qw0-f46.google.com ([209.85.216.46]:57677 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754058Ab0LCXiJ (ORCPT ); Fri, 3 Dec 2010 18:38:09 -0500 Received: by qwb7 with SMTP id 7so10206885qwb.19 for ; Fri, 03 Dec 2010 15:38:08 -0800 (PST) In-Reply-To: <20101203233231.GA29502@8bytes.org> Sender: kvm-owner@vger.kernel.org List-ID: On 12/03/2010 05:32 PM, Joerg Roedel wrote: > On Fri, Dec 03, 2010 at 04:39:22PM -0600, Anthony Liguori wrote: > >> + if (yield_on_hlt) >> + min |= CPU_BASED_HLT_EXITING; >> > This approach won't work out on AMD because in HLT the CPU may enter > C1e. In C1e the local apic timer interupt is not delivered anymore and > when this is the current timer in use the cpu may miss timer ticks or > never comes out of HLT again. The guest has no chance to work around > this as the Linux idle routine does. > And this doesn't break old software on bare metal? Regards, Anthony Liguori > If you really wan't active idling of a guest, it should idle in the > hypervisor where it can work around such problems. > > Joerg > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >