From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:36864)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <borntraeger@de.ibm.com>) id 1SvrFJ-0001O1-NM
	for qemu-devel@nongnu.org; Mon, 30 Jul 2012 10:47:04 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <borntraeger@de.ibm.com>) id 1SvrFF-0000Il-FJ
	for qemu-devel@nongnu.org; Mon, 30 Jul 2012 10:46:57 -0400
Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:40171)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <borntraeger@de.ibm.com>) id 1SvrFF-0000IU-2V
	for qemu-devel@nongnu.org; Mon, 30 Jul 2012 10:46:53 -0400
Received: from /spool/local
	by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use
	Only! Violators will be prosecuted
	for <qemu-devel@nongnu.org> from <borntraeger@de.ibm.com>;
	Mon, 30 Jul 2012 15:46:51 +0100
Received: from d06av09.portsmouth.uk.ibm.com (d06av09.portsmouth.uk.ibm.com
	[9.149.37.250])
	by d06nrmr1707.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with
	ESMTP id q6UEkmw12973744
	for <qemu-devel@nongnu.org>; Mon, 30 Jul 2012 15:46:48 +0100
Received: from d06av09.portsmouth.uk.ibm.com (loopback [127.0.0.1])
	by d06av09.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with
	ESMTP id q6UEkmgq015513
	for <qemu-devel@nongnu.org>; Mon, 30 Jul 2012 08:46:48 -0600
Message-ID: <50169E57.5010203@de.ibm.com>
Date: Mon, 30 Jul 2012 16:46:47 +0200
From: Christian Borntraeger <borntraeger@de.ibm.com>
MIME-Version: 1.0
References: <1343115430-34285-1-git-send-email-borntraeger@de.ibm.com>
	<1343115430-34285-5-git-send-email-borntraeger@de.ibm.com>
	<9EB25248-1A13-4519-A034-DE1707D7FE61@suse.de>
In-Reply-To: <9EB25248-1A13-4519-A034-DE1707D7FE61@suse.de>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 4/7] s390: sclp event support
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: Alexander Graf <agraf@suse.de>
Cc: qemu-devel <qemu-devel@nongnu.org>, blauwirbel@gmail.com, Heinz Graalfs <graalfs@linux.vnet.ibm.com>, Jens Freimann <jfrei@linux.vnet.ibm.com>, afaerber@suse.de

On 30/07/12 15:24, Alexander Graf wrote:

Thanks for the review.

Here is just a short answer regarding the interrupt, we will adress the other comments in a later
mail.

>> void sclp_service_interrupt(uint32_t sccb)
>> {
>> -    if (!sccb) {
>> +    SCLPEventFacility *ef = sbus->event_facility->instance;
>> +    int event_pending = sbus->event_facility->event_pending(ef);
>> +
>> +    if (!event_pending && !sccb) {
>>         return;
>>     }
> 
> Uh. So when there's no event pending no sclp call may trigger an interrupt?

No. If there is no event pending AND no sccb was specified, then we have nothing to report
--> no interrupt.

An service interrupt has a 32bit value as payload. Bits 0-28 (in IBM speak, 31-3 in Linux speak)
contain the sccb address (if any), the other bits are special. The LSB describes if there are still
events pending.

So an unsolicited interrupt will only set the LSB.
An answer to a service call will always contain the sccb and might have the lsb set if there are
events pending.


>> -    s390_sclp_extint(sccb & ~3);
>> +    s390_sclp_extint((sccb & ~3) + event_pending);
> 
> event_pending returns a bool, right? Please make this code a bit less magical :).

Something like "event_pending?1:0" ?