From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:60752)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mark.cave-ayland@ilande.co.uk>) id 1aYsZB-0001h7-WA
	for qemu-devel@nongnu.org; Thu, 25 Feb 2016 04:50:38 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <mark.cave-ayland@ilande.co.uk>) id 1aYsZ8-0006Xi-08
	for qemu-devel@nongnu.org; Thu, 25 Feb 2016 04:50:37 -0500
References: <20160112024421.GH22925@voom.redhat.com>
	<56993062.4030604@ilande.co.uk> <20160118045113.GL9301@voom.fritz.box>
	<56A5B712.9070808@ilande.co.uk>
	<20160125111008.GG32205@voom.redhat.com>
	<56A7F3B7.3080908@ilande.co.uk>
	<20160201005218.GY23043@voom.redhat.com>
	<56B13EB4.9000309@ilande.co.uk> <20160203045926.GH15080@voom.fritz.box>
	<56CCCEAD.70805@ilande.co.uk> <20160224004738.GC2808@voom.fritz.box>
	<87mvqql27q.fsf@emacs.mitica> <56CE8436.6010404@ilande.co.uk>
	<56CE8A7B.60700@ilande.co.uk>
From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-ID: <56CECE5C.4070302@ilande.co.uk>
Date: Thu, 25 Feb 2016 09:50:20 +0000
MIME-Version: 1.0
In-Reply-To: <56CE8A7B.60700@ilande.co.uk>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [Qemu-ppc] Migrating decrementer
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: quintela@redhat.com, David Gibson <david@gibson.dropbear.id.au>
Cc: amit.shah@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org

On 25/02/16 05:00, Mark Cave-Ayland wrote:

> On 25/02/16 04:33, Mark Cave-Ayland wrote:
> 
>> cpu_start/resume():
>>     cpu->tb_env->tb_offset =
>>         qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) * tb_env->tb_freq +
>>             cpu->tb_env->tb_offset -
>>         qemu_clock_get_ns(QEMU_CLOCK_HOST)
> 
> Actually just realised this is slightly wrong and in fact should be:
> 
> cpu_start/resume():
>     cpu->tb_env->tb_offset =
>         muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
>                  cpu->tb_env->tb_freq, NANOSECONDS_PER_SECOND) +
>             cpu->tb_env->tb_offset -
>         qemu_clock_get_ns(QEMU_CLOCK_HOST)

Sign. And let me try that again, this time after caffeine:

cpu_start/resume():
    cpu->tb_env->tb_offset =
        muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
                 cpu->tb_env->tb_freq, NANOSECONDS_PER_SECOND) +
            cpu->tb_env->tb_offset -
        cpu_get_host_ticks();

This should translate to: at CPU start, calculate the difference between
the current guest virtual timebase and the host timebase, storing the
difference in cpu->tb_env->tb_offset.


ATB,

Mark.