From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] Is: axe read_tscp pvops call. Was: Re: [RFC] ACPI S3 and Xen (suprisingly small\!). Date: Thu, 18 Oct 2012 17:31:40 +0100 Message-ID: <50802EEC.6060102@citrix.com> References: <1350481786-4969-1-git-send-email-konrad.wilk@oracle.com> <507ED6C0.4020503@zytor.com> <20121017161036.GA10691@phenom.dumpdata.com> <507EE1C3.7070300@zytor.com> <20121017165452.GA22740@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121017165452.GA22740@phenom.dumpdata.com> Sender: linux-acpi-owner@vger.kernel.org To: Konrad Rzeszutek Wilk Cc: "H. Peter Anvin" , linux-acpi@vger.kernel.org, x86@kernel.org, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, lenb@kernel.org List-Id: xen-devel@lists.xenproject.org On 17/10/12 17:54, Konrad Rzeszutek Wilk wrote: > On Wed, Oct 17, 2012 at 09:50:11AM -0700, H. Peter Anvin wrote: >> On 10/17/2012 09:10 AM, Konrad Rzeszutek Wilk wrote: >>> On Wed, Oct 17, 2012 at 09:03:12AM -0700, H. Peter Anvin wrote: >>>> On 10/17/2012 06:49 AM, Konrad Rzeszutek Wilk wrote: >>>>> >>>>> Note: These are the other patches that went in 3.7-rc1: >>>>> xen/bootup: allow {read|write}_cr8 pvops call [https://lkml.org/lkml/2012/10/10/339] >>>>> xen/bootup: allow read_tscp call for Xen PV guests. [https://lkml.org/lkml/2012/10/10/340] >>>>> >>>> >>>> So WTF do we have a read_tscp PV call? Again, if there isn't a user >>>> we should just axe it... >>> >>> Let me spin off a patch to see if that can be done. >>> >> >> Could you do an audit for other pvops calls that have no users? If >> the *only* user is lguest, we should talk about it, too... > > I can do that - but I don't want to be hasty here. There is a bit of > danger here - for example the read_pmc (or read_tsc) is not in use right > now. But it might be when one starts looking at making perf be able to > analyze the hypervisor (hand-waving the implementation details). So while > removing read_pmc now sounds good, it might be needed in the future. I don't see any reason why would ever need a PV-specific implementation of either read_pmc or read_tsc. And I certainly agree with hpa that leaving them around 'just in case' isn't useful. As for 'perf', since Xen already provides a virtual PMU for HVM guests It's not clear why we would spend the effort to implement another mechanism for PV guests (instead of using the virtual PMU from a PVH guest). David