On Tue, Jun 25, 2019 at 05:36:08PM -0500, Bjorn Helgaas wrote: > Hi Greg, et al, > > Userspace can mmap PCI device memory via the resourceN files in sysfs, > which use pci_mmap_resource(). I think this path is unaware of power > management, so the device may be runtime-suspended, e.g., it may be in > D1, D2, or D3, where it will not respond to memory accesses. > > Userspace accesses while the device is suspended will cause PCI > errors, so I think we need something like the patch below. But this > isn't sufficient by itself because we would need a corresponding > pm_runtime_put() when the mapping goes away. Where should that go? > Or is there a better way to do this? > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > index 6d27475e39b2..aab7a47679a7 100644 > --- a/drivers/pci/pci-sysfs.c > +++ b/drivers/pci/pci-sysfs.c > @@ -1173,6 +1173,7 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr, > > mmap_type = res->flags & IORESOURCE_MEM ? pci_mmap_mem : pci_mmap_io; > > + pm_runtime_get_sync(pdev); > return pci_mmap_resource_range(pdev, bar, vma, mmap_type, write_combine); > } > Ugh, we never thought about this when adding the mmap sysfs interface all those years ago :( I think you are right, this will not properly solve the issue, but I don't know off the top of my head where to solve this. Maybe Rafael has a better idea as he knows the pm paths much better than I do? thanks, greg k-h
