From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: New CPUID/MSR driver; virtualization hooks Date: Thu, 05 Apr 2007 15:31:18 -0700 Message-ID: <461578B6.6020908@zytor.com> References: <461447F2.9010807@zytor.com> <20070405011640.GL19575@sequoia.sous-sol.org> <46144FA6.1000802@zytor.com> <4614867C.4060506@vmware.com> <461539DF.6010502@zytor.com> <46156591.8080802@vmware.com> <46156783.9030501@zytor.com> <461569B7.7060008@vmware.com> <46156CC2.7080600@zytor.com> <46156D95.4070001@vmware.com> <46156EDC.8080403@goop.org> <46157146.1090406@zytor.com> <461575FB.9080508@xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <461575FB.9080508@xensource.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jeremy Fitzhardinge Cc: Chris Wright , Virtualization Mailing List List-Id: virtualization@lists.linuxfoundation.org Jeremy Fitzhardinge wrote: > H. Peter Anvin wrote: >> Yes, pretty much. There are enough evidence that you can't trust CPU = >> architecture to stay sane. Inside Transmeta it was a constant battle, = >> and we were a small company. >> = > = > Is there any indication that the msr or cpuid instructions will change > in this way? rd/wrmsr is pretty explicitly documented as taking the msr > in %ecx, and the value in %edx:eax; do you think that will change? And > likewise cpuid? CPUID already has changed: some CPUID levels are sensitive to %ecx event = though CPUID was originally documented as being sensitive only to %eax, = and I know from personal experience that there are undocumented CPUID = levels in the wild which are sensitive to %ebx. I can't say for sure = (at least on the record) if there are MSRs with nonarchitectural = sensitivities in the wild, but if there aren't, I can guarantee that it = will happen sooner or later, if only because some junior microcode = designer thought it was a great idea. -hpa