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[72.137.123.47]) by smtp.gmail.com with ESMTPSA id s45sm725970qte.26.2020.05.23.12.34.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 May 2020 12:34:18 -0700 (PDT) Date: Sat, 23 May 2020 15:34:17 -0400 From: Peter Xu To: Alex Williamson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, jgg@ziepe.ca, cai@lca.pw Subject: Re: [PATCH v3 3/3] vfio-pci: Invalidate mmaps and block MMIO access on disabled memory Message-ID: <20200523193417.GI766834@xz-x1> References: <159017449210.18853.15037950701494323009.stgit@gimli.home> <159017506369.18853.17306023099999811263.stgit@gimli.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <159017506369.18853.17306023099999811263.stgit@gimli.home> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi, Alex, On Fri, May 22, 2020 at 01:17:43PM -0600, Alex Williamson wrote: > @@ -1346,15 +1526,32 @@ static vm_fault_t vfio_pci_mmap_fault(struct vm_fault *vmf) > { > struct vm_area_struct *vma = vmf->vma; > struct vfio_pci_device *vdev = vma->vm_private_data; > + vm_fault_t ret = VM_FAULT_NOPAGE; > + > + mutex_lock(&vdev->vma_lock); > + down_read(&vdev->memory_lock); I remembered to have seen the fault() handling FAULT_FLAG_RETRY_NOWAIT at least in the very first version, but it's not here any more... Could I ask what's the reason behind? I probably have missed something along with the versions, I'm just not sure whether e.g. this would potentially block a GUP caller even if it's with FOLL_NOWAIT. Side note: Another thing I thought about when reading this patch - there seems to have quite some possibility that the VFIO_DEVICE_PCI_HOT_RESET ioctl will start to return -EBUSY now. Not a problem for this series, but maybe we should rememeber to let the userspace handle -EBUSY properly as follow up too, since I saw QEMU seemed to not handle -EBUSY for host reset path right now. Thanks, -- Peter Xu