From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [Xen-devel] Re: Regression in 3.1 causes Xen to use wrong idle routine Date: Mon, 14 Nov 2011 13:19:01 -0500 Message-ID: <20111114181901.GA14966@phenom.dumpdata.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org To: Keir Fraser Cc: Len Brown , Stefan Bader , "linux-acpi@vger.kernel.org" , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Sun, Nov 13, 2011 at 04:59:10PM +0000, Keir Fraser wrote: > 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 I can't seem to find anything in there advertising the MWAIT feature. > relying on the OSPM in dom0 kernel to parse out Cx/Px info which Xen itself > *can* use. The Cx/Px patches that would parse the Cx/Px and then percolate those up to the hypervisor are in mainline. So that is not it.