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Fri, 20 Sep 2019 15:53:44 GMT Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CEBB67805E; Fri, 20 Sep 2019 15:53:43 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1C9E37805C; Fri, 20 Sep 2019 15:53:42 +0000 (GMT) Received: from oc4221205838.ibm.com (unknown [9.85.141.73]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 20 Sep 2019 15:53:41 +0000 (GMT) Subject: Re: [PATCH v4 4/4] vfio: pci: Using a device region to retrieve zPCI information To: Cornelia Huck References: <1567815231-17940-1-git-send-email-mjrosato@linux.ibm.com> <1567815231-17940-5-git-send-email-mjrosato@linux.ibm.com> <20190919172505.2eb075f8.cohuck@redhat.com> <20190920162607.16198c92.cohuck@redhat.com> From: Matthew Rosato Openpgp: preference=signencrypt Message-ID: Date: Fri, 20 Sep 2019 11:53:41 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190920162607.16198c92.cohuck@redhat.com> Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-09-20_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909200144 Cc: gor@linux.ibm.com, linux-s390@vger.kernel.org, walling@linux.ibm.com, alex.williamson@redhat.com, kvm@vger.kernel.org, sebott@linux.ibm.com, pmorel@linux.ibm.com, heiko.carstens@de.ibm.com, linux-kernel@vger.kernel.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, iommu@lists.linux-foundation.org, robin.murphy@arm.com, gerald.schaefer@de.ibm.com X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On 9/20/19 10:26 AM, Cornelia Huck wrote: > On Thu, 19 Sep 2019 16:57:10 -0400 > Matthew Rosato wrote: > >> On 9/19/19 11:25 AM, Cornelia Huck wrote: >>> On Fri, 6 Sep 2019 20:13:51 -0400 >>> Matthew Rosato wrote: >>> >>>> From: Pierre Morel >>>> >>>> We define a new configuration entry for VFIO/PCI, VFIO_PCI_ZDEV >>>> >>>> When the VFIO_PCI_ZDEV feature is configured we initialize >>>> a new device region, VFIO_REGION_SUBTYPE_ZDEV_CLP, to hold >>>> the information from the ZPCI device the use >>>> >>>> Signed-off-by: Pierre Morel >>>> Signed-off-by: Matthew Rosato >>>> --- >>>> drivers/vfio/pci/Kconfig | 7 +++ >>>> drivers/vfio/pci/Makefile | 1 + >>>> drivers/vfio/pci/vfio_pci.c | 9 ++++ >>>> drivers/vfio/pci/vfio_pci_private.h | 10 +++++ >>>> drivers/vfio/pci/vfio_pci_zdev.c | 85 +++++++++++++++++++++++++++++++++++++ >>>> 5 files changed, 112 insertions(+) >>>> create mode 100644 drivers/vfio/pci/vfio_pci_zdev.c >>>> >>>> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig >>>> index ac3c1dd..d4562a8 100644 >>>> --- a/drivers/vfio/pci/Kconfig >>>> +++ b/drivers/vfio/pci/Kconfig >>>> @@ -45,3 +45,10 @@ config VFIO_PCI_NVLINK2 >>>> depends on VFIO_PCI && PPC_POWERNV >>>> help >>>> VFIO PCI support for P9 Witherspoon machine with NVIDIA V100 GPUs >>>> + >>>> +config VFIO_PCI_ZDEV >>>> + bool "VFIO PCI Generic for ZPCI devices" >>>> + depends on VFIO_PCI && S390 >>>> + default y >>>> + help >>>> + VFIO PCI support for S390 Z-PCI devices >>> >>> >From that description, I'd have no idea whether I'd want that or not. >>> Is there any downside to enabling it? >>> >> >> :) Not really, you're just getting information from the hardware vs >> using hard-coded defaults. The only reason I could think of to turn it >> off would be if you wanted/needed to restore this hard-coded behavior. > > I'm not really sure whether that's worth adding a Kconfig switch for. > Won't older versions simply ignore the new region anyway? > Yes, you have a point here... This switch showed up in v3 of this series when Pierre changed to using a region to pass this info and I haven't yet found a 'why' he decided to add the Kconfig switch. If I can't convince myself of a reason to keep it, I'll just remove it from the next version. > Also, I don't think we have any migration compatibility issues, as > vfio-pci devices are not (yet) migrateable anyway. > >> >> bool "VFIO PCI support for generic ZPCI devices" ? > > "Support zPCI-specific configuration for VFIO PCI" ? > >> >> "Support for sharing ZPCI hardware device information between the host >> and guests." ? > > "Enabling this options exposes a region containing hardware > configuration for zPCI devices. This enables userspace (e.g. QEMU) to > supply proper configuration values instead of hard-coded defaults for > zPCI devices passed through via VFIO on s390. > > Say Y here." > > ? > Your descriptions are much better - thanks for the feedback! _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu