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Tue, 28 Jul 2020 09:33:56 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 45B7AAE053; Tue, 28 Jul 2020 09:33:56 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9BCC9AE059; Tue, 28 Jul 2020 09:33:55 +0000 (GMT) Received: from oc5500677777.ibm.com (unknown [9.145.68.234]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 28 Jul 2020 09:33:55 +0000 (GMT) Subject: Re: [RFC PATCH] s390x/pci: vfio-pci breakage with disabled mem enforcement To: Alex Williamson , Pierre Morel References: <1595517236-17823-1-git-send-email-mjrosato@linux.ibm.com> <20200723102916.7cf15b43@w520.home> <0481c77e-f71f-886b-9b0a-41529eb139ee@linux.ibm.com> <20200727104754.4337818c@x1.home> From: Niklas Schnelle Message-ID: Date: Tue, 28 Jul 2020 11:33:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200727104754.4337818c@x1.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-28_01:2020-07-28, 2020-07-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 lowpriorityscore=0 mlxscore=0 spamscore=0 clxscore=1015 malwarescore=0 suspectscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007280069 Received-SPF: pass client-ip=148.163.156.1; envelope-from=schnelle@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/28 04:59:18 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Matthew Rosato , david@redhat.com, cohuck@redhat.com, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/27/20 6:47 PM, Alex Williamson wrote: > On Mon, 27 Jul 2020 17:40:39 +0200 > Pierre Morel wrote: > >> On 2020-07-23 18:29, Alex Williamson wrote: >>> On Thu, 23 Jul 2020 11:13:55 -0400 >>> Matthew Rosato wrote: >>> >>>> I noticed that after kernel commit abafbc55 'vfio-pci: Invalidate mmaps >>>> and block MMIO access on disabled memory' vfio-pci via qemu on s390x >>>> fails spectacularly, with errors in qemu like: ... snip ... >> >> Alex, Matt, >> >> in s390 we have the possibility to assign a virtual function to a >> logical partition as function 0. >> In this case it can not be treated as a virtual function but must be >> treated as a physical function. >> This is currently working very well. >> However, these functions do not set PCI_COMMAND_MEMORY as we need. > > Where is the vendor and device ID virtualization done for these > devices, we can't have a PF with IDs 0000:0000. Pierre doesn't mean the Device/Vendor IDs he means it has devfn == 0 so it is the mandatory function zero on it's PCI bus, where until recently we always had only one function per bus but with the recent multi-function support it can act more like on other platforms with several PCI functions sharing the same Bus e.g. a PF and the VFs created through sriov_numvfs. That's why I'm saying that having devfn == 0 should not be very special for a VF passed to a VM and I really don't see where it would not act like a VF passed from any other Hypervisor. The only really tricky part in my opinion is where during the "probing" we do set is_virtfn so it happens both for VFs passed-through from z/VM or LPAR and VFs created through sriov_numvfs which unlike on other platforms are also scanned by Firmware (pdev->no_vf_scan disables the Linux side scanning). With the fix I'm currently testing I had to do this in pcibios_enable_device() because I also create sysfs links between VFs and their parent PFs and those need the sysfs entries to be already created, which makes the more apropriately sound pcibios_bus_add_device() too early. > >> Shouldn't we fix this inside the kernel, to keep older QMEU working? >> >> Then would it be OK to add a new bit/boolean inside the >> pci_dev/vfio_pci_device like, is_detached_vfn, that we could set during >> enumeration and test inside __vfio_pci_memory_enabled() to return true? > > Probably each instance of is_virtfn in vfio-pci should be looked at to > see if it applies to s390. If we're going to recognize this as a VF, > I'd rather we complete the emulation that the lower level hypervisor > has missed. If we can enable all the is_virtfn code on s390, then we > should probably cache is_virtfn on the vfio_pci_device object and allow > s390 a place to set it once at probe or enable time. > >> In the enumeration we have the possibility to know if the function is a >> HW/Firmware virtual function on devfn 0 or if it is created by SRIOV. >> >> It seems an easy fix without side effects. >> >> What do you think? > > It sure seems preferable to recognize that it is a VF in the kernel > than to require userspace to have arch specific hacks. Thanks, > > Alex >