| Message ID | 20190625223608.GB103694@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | mmap/munmap in sysfs | expand |
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
On Wednesday, June 26, 2019 3:07:46 AM CEST Greg Kroah-Hartman wrote: > 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? Well, let me think about this a bit.
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); }