From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [Xen-devel] Re: Regression in 3.1 causes Xen to use wrong idle routine Date: Sun, 13 Nov 2011 16:59:10 +0000 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org To: Len Brown , Stefan Bader Cc: "linux-acpi@vger.kernel.org" , "xen-devel@lists.xensource.com" , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On 13/11/2011 03:46, "Len Brown" wrote: >> The problem I see is that select_idle_routine() is called from >> arch/x86/kernel/cpu/common.c and since Xen setup does not set pm_idle >> anymore, it can cause mwait_idle or amd_e400_idle functions to be selected. >> In testing it seem amd_e400_idle in PVM domU at least does not immediately >> cause >> problems, but mwait_idle just causes crashes. From the reports I have >> this may be related to older hypervisors (3.1 and older) not clearing the >> mwait >> capability. But overall there seems something wrong in the interaction. > > Why is Xen advertising X86_FEATURE_MWAIT and then crashing > when the dom0 (or other guests) use what it advertises? > > What versions of Xen have this bug? Xen doesn't advertise MWAIT. Possibly Xen-pv_ops is lying to the rest of the kernel via the cpuid pv_ops hook. This would probably be because Xen is relying on the OSPM in dom0 kernel to parse out Cx/Px info which Xen itself *can* use. -- Keir