From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:46995)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1X5d4k-0000CB-OG
	for qemu-devel@nongnu.org; Fri, 11 Jul 2014 11:49:38 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1X5d4d-0006oc-9d
	for qemu-devel@nongnu.org; Fri, 11 Jul 2014 11:49:30 -0400
Received: from mx1.redhat.com ([209.132.183.28]:45666)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1X5d4d-0006no-1r
	for qemu-devel@nongnu.org; Fri, 11 Jul 2014 11:49:23 -0400
Message-ID: <53C00776.6090406@redhat.com>
Date: Fri, 11 Jul 2014 17:49:10 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1405064666-5359-1-git-send-email-drjones@redhat.com>
	<53C002FB.3000805@redhat.com>
In-Reply-To: <53C002FB.3000805@redhat.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH] backends: Introduce chr-testdev
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: Eric Blake <eblake@redhat.com>, Andrew Jones <drjones@redhat.com>, qemu-devel@nongnu.org
Cc: kvmarm@lists.cs.columbia.edu, christoffer.dall@linaro.org

Il 11/07/2014 17:30, Eric Blake ha scritto:
> On 07/11/2014 01:44 AM, Andrew Jones wrote:
>> From: Paolo Bonzini <pbonzini@redhat.com>
>>
>> From: Paolo Bonzini <pbonzini@redhat.com>
>>
>> chr-testdev enables a virtio serial channel to be used for guest
>> initiated qemu exits. hw/misc/debugexit already enables guest
>> initiated qemu exits, but only for PC targets. chr-testdev supports
>> any virtio-capable target. kvm-unit-tests/arm is already making use
>> of this backend.
>>
>> Currently there is a single command implemented, "q".  It takes a
>> (prefix) argument for the exit code, thus an exit is implemented by
>> writing, e.g. "1q", to the virtio-serial port.
>>
>> It can be used as:
>>    $QEMU ... \
>>      -device virtio-serial-device \
>>      -device virtserialport,chardev=ctd -chardev testdev,id=ctd
>>
>> or, use:
>>    $QEMU ... \
>>      -device virtio-serial-device \
>>      -device virtconsole,chardev=ctd -chardev testdev,id=ctd
>>
>> to bind it to virtio-serial port0.
>>
>
>> +
>> +    switch (c) {
>> +    case 'q':
>> +        exit((arg << 1) | 1);
>> +        break;
>
> I'm trying to figure out the motive for only exiting with odd numbers.
> That is, 'q' => 1, '1q' => 3, '2q' => 5, '3q' => 7.  It means that at
> most, I can do '127q' => 255 before I suffer from exit() limiting things
> to 8 bits.  This wasn't explained in the commit message.

It's just for parity with isa-debugexit.

Paolo