From mboxrd@z Thu Jan 1 00:00:00 1970 From: Holger Steinhaus Subject: Writing MSRs from Domain0 Date: Fri, 06 Oct 2006 11:11:16 +0200 Message-ID: <45261DB4.8000009@gmx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Hello, I recently tried Xen 3.0.3-testing on my 2x Opteron-244 SMP machine. Everything works well exept one detail, which is not unimportant to me: the powernow-k8 driver fails to switch frequencies. A closer look on the powernow-k8 source reveals, that some MSR write operations seem to be without any effect. A rdmsr() before and after the wrmsr() call reveals that no real change on the register ocurrs. An older PowerNow patch from this list emulates MSR writes by DOM0_MSR hypercalls, but this call seems to be abandoned some time ago. Other routines in the kernel simply employ the rdmsr()/wrmsr() macros from the Linux kernel, as the current PowerNow drivers does. Whats the correct Xen-like way to maniputate a MSR from a Domain0? Regards, Holger