From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v1] kvm/x86: Hyper-V tsc page setup Date: Fri, 22 Jan 2016 12:53:26 +0100 Message-ID: <56A21836.1010204@redhat.com> References: <1450949580-25759-1-git-send-email-asmetanin@virtuozzo.com> <56A1FF8F.3050701@redhat.com> <56A20131.8090102@virtuozzo.com> <56A20C30.4020608@redhat.com> <56A212F9.4030800@virtuozzo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Roman Kagan , "Denis V. Lunev" , qemu-devel@nongnu.org To: asmetanin@virtuozzo.com, kvm@vger.kernel.org Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:34741 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752733AbcAVLxa (ORCPT ); Fri, 22 Jan 2016 06:53:30 -0500 Received: by mail-wm0-f66.google.com with SMTP id b14so16837876wmb.1 for ; Fri, 22 Jan 2016 03:53:29 -0800 (PST) In-Reply-To: <56A212F9.4030800@virtuozzo.com> Sender: kvm-owner@vger.kernel.org List-ID: On 22/01/2016 12:31, Andrey Smetanin wrote: >> >> Sometimes the TSC is detected to be unstable and Linux switches to >> another clocksource. At least in that case you can get a write to the >> TSC page while the guest is running. > Sorry, now I got it, you mean host TSC is unstable and we should mark > guest tsc page invalid. Now I understand please ignore my prev. message. No problem. Anyhow yes, this is what I meant: a host write to the TSC page, not a guest write to the TSC page MSR. Usually it happens only at migration time to update the sequence---which I believe your patch wasn't doing either. But if we tie TSC page updates to kvm_gen_update_masterclock, we get that for free when the migration destination calls the KVM_SET_CLOCK ioctl. Paolo