From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48121) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMaHV-0001jv-JP for qemu-devel@nongnu.org; Fri, 22 Jan 2016 06:53:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aMaHS-0002Oi-94 for qemu-devel@nongnu.org; Fri, 22 Jan 2016 06:53:33 -0500 Received: from mail-wm0-x241.google.com ([2a00:1450:400c:c09::241]:35142) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMaHS-0002Oe-1Z for qemu-devel@nongnu.org; Fri, 22 Jan 2016 06:53:30 -0500 Received: by mail-wm0-x241.google.com with SMTP id 123so16799765wmz.2 for ; Fri, 22 Jan 2016 03:53:29 -0800 (PST) Sender: Paolo Bonzini 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> From: Paolo Bonzini Message-ID: <56A21836.1010204@redhat.com> Date: Fri, 22 Jan 2016 12:53:26 +0100 MIME-Version: 1.0 In-Reply-To: <56A212F9.4030800@virtuozzo.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v1] kvm/x86: Hyper-V tsc page setup List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: asmetanin@virtuozzo.com, kvm@vger.kernel.org Cc: Gleb Natapov , "Denis V. Lunev" , Roman Kagan , qemu-devel@nongnu.org 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