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Fri, 28 Feb 2025 21:56:37 GMT Received: from smtpav03.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 865B358056; Fri, 28 Feb 2025 21:56:37 +0000 (GMT) Received: from smtpav03.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 289405803F; Fri, 28 Feb 2025 21:56:36 +0000 (GMT) Received: from [9.61.46.135] (unknown [9.61.46.135]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Fri, 28 Feb 2025 21:56:36 +0000 (GMT) Message-ID: <8cff6617-634c-4e10-bd1d-7719edf484ea@linux.ibm.com> Date: Fri, 28 Feb 2025 16:56:35 -0500 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/3] s390/pci: Fix s390_mmio_read/write syscall page fault handling To: Niklas Schnelle , Bjorn Helgaas , Christoph Hellwig , Alexandra Winter , Alex Williamson , Gerd Bayer , Jason Gunthorpe , Thorsten Winkler , Bjorn Helgaas Cc: Julian Ruess , Halil Pasic , Christian Borntraeger , Sven Schnelle , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-pci@vger.kernel.org References: <20250226-vfio_pci_mmap-v7-0-c5c0f1d26efd@linux.ibm.com> <20250226-vfio_pci_mmap-v7-1-c5c0f1d26efd@linux.ibm.com> Content-Language: en-US From: Matthew Rosato In-Reply-To: <20250226-vfio_pci_mmap-v7-1-c5c0f1d26efd@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: hOaKjlQZxMFi8CAbzE3LfAeOcKj-Pidr X-Proofpoint-ORIG-GUID: OA0cRxaMfrKCLZAKccGnkHvvkihMq1rK X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-28_06,2025-02-28_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 impostorscore=0 spamscore=0 priorityscore=1501 mlxlogscore=923 mlxscore=0 lowpriorityscore=0 clxscore=1011 bulkscore=0 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502280156 On 2/26/25 7:07 AM, Niklas Schnelle wrote: > The s390 MMIO syscalls when using the classic PCI instructions do not > cause a page fault when follow_pfnmap_start() fails due to the page not > being present. Besides being a general deficiency this breaks vfio-pci's > mmap() handling once VFIO_PCI_MMAP gets enabled as this lazily maps on > first access. Fix this by following a failed follow_pfnmap_start() with > fixup_user_page() and retrying the follow_pfnmap_start(). Also fix > a VM_READ vs VM_WRITE mixup in the read syscall. > > Signed-off-by: Niklas Schnelle Reviewed-by: Matthew Rosato