Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751700Ab3IRFoH (ORCPT ); Wed, 18 Sep 2013 01:44:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59329 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256Ab3IRFoF (ORCPT ); Wed, 18 Sep 2013 01:44:05 -0400 Date: Wed, 18 Sep 2013 08:43:35 +0300 From: Gleb Natapov To: KY Srinivasan Cc: "H. Peter Anvin" , "x86@kernel.org" , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "jasowang@redhat.com" , "tglx@linutronix.de" , "JBeulich@suse.com" , "bp@alien8.de" Subject: Re: [PATCH V2 1/1] X86: Hyper-V: Get the local APIC timer frequency from the hypervisor Message-ID: <20130918054335.GE5657@redhat.com> References: <1378233023-4512-1-git-send-email-kys@microsoft.com> <52325C1E.90101@zytor.com> <50f92d9c16a54e5bb6fa14ef72e5fdfb@SN2PR03MB061.namprd03.prod.outlook.com> <20130913095526.GE18381@redhat.com> <7737cb643a664b6fb39021b4d364b5cf@SN2PR03MB061.namprd03.prod.outlook.com> <20130917135918.GY17294@redhat.com> <2b4a9a0cff5143c59a0802a2e425c4db@SN2PR03MB061.namprd03.prod.outlook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2b4a9a0cff5143c59a0802a2e425c4db@SN2PR03MB061.namprd03.prod.outlook.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1096 Lines: 24 On Tue, Sep 17, 2013 at 07:53:36PM +0000, KY Srinivasan wrote: > > > Thanks Gleb. Here is the link for the latest Hyper-V specification: > > > http://www.microsoft.com/en-us/download/details.aspx?id=39289 > > > > > > This spec talks about how migration is handled with regards to TSC. > > > > > All I can see is "15.4.3 Partition Reference TSC Mechanism". I see > > nothing about HV_X64_MSR_TSC_FREQUENCY specifically. To access this MSR > > a partition needs AccessFrequencyMsrs privilege, may be partition that > > cab be migrated does not have this privilege? > > If you use the MSR to read the TSC frequency, then indeed when you migrate then there > is no guarantee that the TSC frequency won't change when you migrate. The approach > described in section 15.4.3 is the preferred approach that can accommodate migration. > Thanks. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/