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Wed, 9 Dec 2020 20:52:46 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6A686112062; Wed, 9 Dec 2020 20:52:44 +0000 (GMT) Received: from oc4221205838.ibm.com (unknown [9.163.37.122]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 9 Dec 2020 20:52:44 +0000 (GMT) Subject: Re: [RFC 0/4] vfio-pci/zdev: Fixing s390 vfio-pci ISM support From: Matthew Rosato To: alex.williamson@redhat.com, cohuck@redhat.com, schnelle@linux.ibm.com Cc: pmorel@linux.ibm.com, borntraeger@de.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <1607545670-1557-1-git-send-email-mjrosato@linux.ibm.com> Message-ID: <765a8b73-a879-ea96-d13e-8fd574b363be@linux.ibm.com> Date: Wed, 9 Dec 2020 15:52:43 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <1607545670-1557-1-git-send-email-mjrosato@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-09_16:2020-12-09,2020-12-09 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxlogscore=999 mlxscore=0 spamscore=0 lowpriorityscore=0 phishscore=0 impostorscore=0 adultscore=0 suspectscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012090140 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 12/9/20 3:27 PM, Matthew Rosato wrote: > Today, ISM devices are completely disallowed for vfio-pci passthrough as > QEMU will reject the device due to an (inappropriate) MSI-X check. > However, in an effort to enable ISM device passthrough, I realized that the > manner in which ISM performs block write operations is highly incompatible > with the way that QEMU s390 PCI instruction interception and > vfio_pci_bar_rw break up I/O operations into 8B and 4B operations -- ISM > devices have particular requirements in regards to the alignment, size and > order of writes performed. Furthermore, they require that legacy/non-MIO > s390 PCI instructions are used, which is also not guaranteed when the I/O > is passed through the typical userspace channels. > > As a result, this patchset proposes a new VFIO region to allow a guest to > pass certain PCI instruction intercepts directly to the s390 host kernel > PCI layer for exeuction, pinning the guest buffer in memory briefly in > order to execute the requested PCI instruction. > > Matthew Rosato (4): > s390/pci: track alignment/length strictness for zpci_dev > vfio-pci/zdev: Pass the relaxed alignment flag > s390/pci: Get hardware-reported max store block length > vfio-pci/zdev: Introduce the zPCI I/O vfio region > > arch/s390/include/asm/pci.h | 4 +- > arch/s390/include/asm/pci_clp.h | 7 +- > arch/s390/pci/pci_clp.c | 2 + > drivers/vfio/pci/vfio_pci.c | 8 ++ > drivers/vfio/pci/vfio_pci_private.h | 6 ++ > drivers/vfio/pci/vfio_pci_zdev.c | 160 ++++++++++++++++++++++++++++++++++++ > include/uapi/linux/vfio.h | 4 + > include/uapi/linux/vfio_zdev.h | 33 ++++++++ > 8 files changed, 221 insertions(+), 3 deletions(-) > Associated qemu patchset: https://lists.gnu.org/archive/html/qemu-devel/2020-12/msg02377.html