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Fri, 24 Jul 2020 09:46:40 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B664052054; Fri, 24 Jul 2020 09:46:40 +0000 (GMT) Received: from oc5500677777.ibm.com (unknown [9.145.155.57]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id C990D52051; Fri, 24 Jul 2020 09:46:39 +0000 (GMT) Subject: Re: [RFC PATCH] s390x/pci: vfio-pci breakage with disabled mem enforcement To: Matthew Rosato , alex.williamson@redhat.com, pmorel@linux.ibm.com References: <1595517236-17823-1-git-send-email-mjrosato@linux.ibm.com> From: Niklas Schnelle Message-ID: <050f39c7-a670-7592-ee50-fef6ea4bdb0f@linux.ibm.com> Date: Fri, 24 Jul 2020 11:46:39 +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: <1595517236-17823-1-git-send-email-mjrosato@linux.ibm.com> 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=2020-07-24_02:2020-07-24, 2020-07-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 phishscore=0 adultscore=0 clxscore=1011 priorityscore=1501 mlxscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007240068 Received-SPF: pass client-ip=148.163.158.5; envelope-from=schnelle@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/24 05:46:46 X-ACL-Warn: Detected OS = Linux 3.x [generic] 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, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Fri, 24 Jul 2020 09:54:21 -0400 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: 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 7/23/20 5:13 PM, 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: > > qemu-system-s390x: vfio_region_read(0001:00:00.0:region0+0x0, 4) failed: Input/output error > > From read to bar 0 originating out of hw/s390x/s390-pci-inst.c:zpci_read_bar(). > > So, I'm trying to figure out how to get vfio-pci happy again on s390x. From > a bit of tracing, we seem to be triggering the new trap in > __vfio_pci_memory_enabled(). Sure enough, if I just force this function to > return 'true' as a test case, things work again. > The included patch attempts to enforce the setting, which restores everything > to working order but also triggers vfio_bar_restore() in the process.... So > this isn't the right answer, more of a proof-of-concept. > > @Alex: Any guidance on what needs to happen to make qemu-s390x happy with this > recent kernel change? > > @Nilkas/@Pierre: I wonder if this might be related to host device is_virtfn? > I note that my host device lspci output looks like: > > 0000:00:00.0 Ethernet controller: Mellanox Technologies MT27710 Family [ConnectX-4 Lx Virtual Function] > > But the device is not marked as is_virtfn.. Otherwise, Alex's fix > from htps://lkml.org/lkml/2020/6/25/628 should cover the case. With commit e5794cf1a270 ("s390/pci: create links between PFs and VFs") I introduced the is_physfn field to struct zpci_dev which gets set through the CLP Query PCI Function. Also with that commit this being 0 will set is_virtfn to 1. Interestingly looking at s390-pci-inst.c in QEMU I'd think that on QEMU this should already be 0 and thus is_virtfn should be set with Linux >5.8-rc1 and the missing case is actually for passing through a PF where it would wrongly be 0 too. Note: If the Linux instance does not see the parent PF however the only way I know to test if it is a VF from userspace is checking if /sys/bus/pci/devices//vfn is non-zero which is platform specific and currently wrongly set 0 on QEMU for VFs. If the PF is known the mentioned commit will also create the /sys/bus/pci/devices//physfn symlink as on other platforms. > Matthew Rosato (1): > s390x/pci: Enforce PCI_COMMAND_MEMORY for vfio-pci > > hw/s390x/s390-pci-inst.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) >