From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:61382 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726008AbgDXDNZ (ORCPT ); Thu, 23 Apr 2020 23:13:25 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 03O2VpQS007970 for ; Thu, 23 Apr 2020 23:13:24 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 30kppdj383-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 23 Apr 2020 23:13:24 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 24 Apr 2020 04:12:56 +0100 Date: Fri, 24 Apr 2020 05:13:15 +0200 From: Halil Pasic Subject: Re: [PATCH v7 04/15] s390/vfio-ap: implement in-use callback for vfio_ap driver In-Reply-To: <5cf7d611-e30c-226d-0d3d-d37170f117f4@linux.ibm.com> References: <20200407192015.19887-1-akrowiak@linux.ibm.com> <20200407192015.19887-5-akrowiak@linux.ibm.com> <20200416131845.3ef6b3b5.cohuck@redhat.com> <5cf7d611-e30c-226d-0d3d-d37170f117f4@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Message-Id: <20200424051315.20f17133.pasic@linux.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Tony Krowiak Cc: Cornelia Huck , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@linux.ibm.com, borntraeger@de.ibm.com, mjrosato@linux.ibm.com, pmorel@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, jjherne@linux.ibm.com, fiuczy@linux.ibm.com On Thu, 16 Apr 2020 10:45:20 -0400 Tony Krowiak wrote: > > > On 4/16/20 7:18 AM, Cornelia Huck wrote: > > On Tue, 7 Apr 2020 15:20:04 -0400 > > Tony Krowiak wrote: > > > >> Let's implement the callback to indicate when an APQN > >> is in use by the vfio_ap device driver. The callback is > >> invoked whenever a change to the apmask or aqmask would > >> result in one or more queue devices being removed from the driver. The > >> vfio_ap device driver will indicate a resource is in use > >> if the APQN of any of the queue devices to be removed are assigned to > >> any of the matrix mdevs under the driver's control. > >> > >> Signed-off-by: Tony Krowiak > >> --- > >> drivers/s390/crypto/vfio_ap_drv.c | 1 + > >> drivers/s390/crypto/vfio_ap_ops.c | 47 +++++++++++++++++---------- > >> drivers/s390/crypto/vfio_ap_private.h | 2 ++ > >> 3 files changed, 33 insertions(+), 17 deletions(-) > >> @@ -1369,3 +1371,14 @@ void vfio_ap_mdev_remove_queue(struct ap_queue *queue) > >> kfree(q); > >> mutex_unlock(&matrix_dev->lock); > >> } > >> + > >> +bool vfio_ap_mdev_resource_in_use(unsigned long *apm, unsigned long *aqm) > >> +{ > >> + bool in_use; > >> + > >> + mutex_lock(&matrix_dev->lock); > >> + in_use = vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm) ? true : false; > > Maybe > > > > in_use = !!vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm); > > > > ? > > To be honest, I find the !! expression very confusing. Every time I see > it, I have > to spend time thinking about what the result of !! is going to be. I think > the statement should be left as-is because it more clearly expresses > the intent. > This is discussion is just about cosmetics, I believe. Just a piece of advice: try to be sensitive about the community. In this community, and I believe in C general !! is the idiomatic way to convert number to boolean. Why would one want to do that is a bit longer story. The short version is in logic condition context the value 0 is false and any other value is true. !! keeps false value (0) false, and forces a true to the most true true value. If you keep getting confused every time you run across a !! that won't help with reading other peoples C. Regards, Halil > > > >> + mutex_unlock(&matrix_dev->lock); > >> + > >> + return in_use; > >> +} >