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Fri, 14 Feb 2025 13:11:01 +0000 (GMT) From: Niklas Schnelle Date: Fri, 14 Feb 2025 14:10:52 +0100 Subject: [PATCH v6 1/3] s390/pci: Fix s390_mmio_read/write syscall page fault handling Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20250214-vfio_pci_mmap-v6-1-6f300cb63a7e@linux.ibm.com> References: <20250214-vfio_pci_mmap-v6-0-6f300cb63a7e@linux.ibm.com> In-Reply-To: <20250214-vfio_pci_mmap-v6-0-6f300cb63a7e@linux.ibm.com> To: Bjorn Helgaas , Christoph Hellwig , Alexandra Winter , Alex Williamson , Gerd Bayer , Matthew Rosato , 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, Niklas Schnelle X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2001; i=schnelle@linux.ibm.com; h=from:subject:message-id; bh=QnE3MWbyEccydmUgWLoslOgDk1WgUiqPUae/4stuq/o=; b=owGbwMvMwCX2Wz534YHOJ2GMp9WSGNLXO9zfKNCZ3LWfy6qHd7uM77EjCm1e0/qmeMk+1Hw42 eHukvv/O0pZGMS4GGTFFFkWdTn7rSuYYronqL8DZg4rE8gQBi5OAZiIjiUjwwTXwtapG86ujD0o /3RKWTbP08DbDD+kHtycIjF7aqyZVSkjw8/ipbHCcas5Ns0+XcE6d63YspzXH50afY1YC3d9eNj WwgoA X-Developer-Key: i=schnelle@linux.ibm.com; a=openpgp; fpr=9DB000B2D2752030A5F72DDCAFE43F15E8C26090 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: WFaV4Qu094bww62jFQbPfuU1rdkxorfX X-Proofpoint-ORIG-GUID: a4BLbTqTnfySI6XOyiNN32nHh0Ng0Ziq 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=2025-02-14_05,2025-02-13_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 mlxscore=0 spamscore=0 bulkscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 impostorscore=0 mlxlogscore=890 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2501170000 definitions=main-2502140096 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 --- arch/s390/pci/pci_mmio.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c index 46f99dc164ade4ca10f170cd66bdb648f92aa904..1997d9b7965df3b9b6019c7537028cd29d52fc13 100644 --- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -175,8 +175,12 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr, args.address = mmio_addr; args.vma = vma; ret = follow_pfnmap_start(&args); - if (ret) - goto out_unlock_mmap; + if (ret) { + fixup_user_fault(current->mm, mmio_addr, FAULT_FLAG_WRITE, NULL); + ret = follow_pfnmap_start(&args); + if (ret) + goto out_unlock_mmap; + } io_addr = (void __iomem *)((args.pfn << PAGE_SHIFT) | (mmio_addr & ~PAGE_MASK)); @@ -315,14 +319,18 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr, if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) goto out_unlock_mmap; ret = -EACCES; - if (!(vma->vm_flags & VM_WRITE)) + if (!(vma->vm_flags & VM_READ)) goto out_unlock_mmap; args.vma = vma; args.address = mmio_addr; ret = follow_pfnmap_start(&args); - if (ret) - goto out_unlock_mmap; + if (ret) { + fixup_user_fault(current->mm, mmio_addr, 0, NULL); + ret = follow_pfnmap_start(&args); + if (ret) + goto out_unlock_mmap; + } io_addr = (void __iomem *)((args.pfn << PAGE_SHIFT) | (mmio_addr & ~PAGE_MASK));