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Wed, 20 Jan 2021 09:02:09 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A49314C046; Wed, 20 Jan 2021 09:02:08 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.145.39.155]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 20 Jan 2021 09:02:08 +0000 (GMT) Subject: Re: [PATCH 0/4] vfio-pci/zdev: Fixing s390 vfio-pci ISM support To: Matthew Rosato , alex.williamson@redhat.com, cohuck@redhat.com, schnelle@linux.ibm.com Cc: 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: <1611086550-32765-1-git-send-email-mjrosato@linux.ibm.com> From: Pierre Morel Message-ID: Date: Wed, 20 Jan 2021 10:02:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <1611086550-32765-1-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=2021-01-20_02:2021-01-18,2021-01-20 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 clxscore=1011 mlxscore=0 suspectscore=0 phishscore=0 spamscore=0 impostorscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101200049 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 1/19/21 9:02 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 execution, pinning the guest buffer in memory briefly in > order to execute the requested PCI instruction. > > Changes from RFC -> v1: > - No functional changes, just minor commentary changes -- Re-posting along > with updated QEMU set. > Hi, there are is a concerns about this patch series: As the title says it is strongly related to ISM hardware. Why being so specific? Regards, Pierre -- Pierre Morel IBM Lab Boeblingen