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Wed, 26 Jun 2024 11:16:24 +0000 (GMT) From: Niklas Schnelle Date: Wed, 26 Jun 2024 13:15:48 +0200 Subject: [PATCH v4 1/4] s390/pci: Fix s390_mmio_read/write syscall page fault handling Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240626-vfio_pci_mmap-v4-1-7f038870f022@linux.ibm.com> References: <20240626-vfio_pci_mmap-v4-0-7f038870f022@linux.ibm.com> In-Reply-To: <20240626-vfio_pci_mmap-v4-0-7f038870f022@linux.ibm.com> To: Bjorn Helgaas , Christoph Hellwig , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Alex Williamson , Gerd Bayer , Matthew Rosato , Jason Gunthorpe Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Niklas Schnelle , Jason Gunthorpe X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1957; i=schnelle@linux.ibm.com; h=from:subject:message-id; bh=kmttkYcl7RaIqBVfs1vIdHpH/R3f9A14cvLyhdB1rck=; 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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_pte() with fixup_user_page() and retrying the follow_pte(). Reviewed-by: Jason Gunthorpe Reviewed-by: Matthew Rosato 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 5398729bfe1b..80c21b1a101c 100644 --- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -170,8 +170,12 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr, goto out_unlock_mmap; ret = follow_pte(vma, mmio_addr, &ptep, &ptl); - if (ret) - goto out_unlock_mmap; + if (ret) { + fixup_user_fault(current->mm, mmio_addr, FAULT_FLAG_WRITE, NULL); + ret = follow_pte(vma, mmio_addr, &ptep, &ptl); + if (ret) + goto out_unlock_mmap; + } io_addr = (void __iomem *)((pte_pfn(*ptep) << PAGE_SHIFT) | (mmio_addr & ~PAGE_MASK)); @@ -305,12 +309,16 @@ 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; ret = follow_pte(vma, mmio_addr, &ptep, &ptl); - if (ret) - goto out_unlock_mmap; + if (ret) { + fixup_user_fault(current->mm, mmio_addr, 0, NULL); + ret = follow_pte(vma, mmio_addr, &ptep, &ptl); + if (ret) + goto out_unlock_mmap; + } io_addr = (void __iomem *)((pte_pfn(*ptep) << PAGE_SHIFT) | (mmio_addr & ~PAGE_MASK));