From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:48914)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vobwv-0006Cg-AI
	for qemu-devel@nongnu.org; Thu, 05 Dec 2013 11:38:57 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vobwp-0005ZL-Au
	for qemu-devel@nongnu.org; Thu, 05 Dec 2013 11:38:49 -0500
Received: from mx1.redhat.com ([209.132.183.28]:12016)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Vobwp-0005ZA-3G
	for qemu-devel@nongnu.org; Thu, 05 Dec 2013 11:38:43 -0500
Message-ID: <52A0AC09.4090202@redhat.com>
Date: Thu, 05 Dec 2013 17:38:33 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1386054500.25757.10.camel@nexus> <529D90A6.2080801@lab.ntt.co.jp>
	<52A0186A.2050207@lab.ntt.co.jp>
	<1386224104.3091.3.camel@nexus> <52A04732.4040105@redhat.com>
	<52A07C5A.9090105@lab.ntt.co.jp> <52A08541.6090702@redhat.com>
	<52A09EF4.5080800@lab.ntt.co.jp> <20131205161707.GB17277@amt.cnet>
In-Reply-To: <20131205161707.GB17277@amt.cnet>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH] target-i386: clear guest TSC on reset
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>, Will Auld <will.auld@intel.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Fernando Luis Vazquez Cao <fernando_b1@lab.ntt.co.jp>

Il 05/12/2013 17:17, Marcelo Tosatti ha scritto:
>> > I agree it is a bit ugly, but in my testing QEMU seemed to loop over all
>> > the VCPUS fast enough for the kernel side kvm_write_tsc() to do a
>> > reasonable job of matching the offsets (the Linux guest did not mark
>> > the TSC unstable due to the TSCs being unsynchronized). Am I missing
>> > something?
> Right, modern kernels (see kvm_write_tsc) perform synchronization, so in
> theory the "KVM is yet unable to synchronize ..." code is not necessary
> anymore.
> 
> I vote for dropping the thing entirely.

If it can be dropped entirely, I certainly have no problem with starting
with a simple patch first.

Paolo