* mmap/munmap in sysfs
@ 2019-06-25 22:36 Bjorn Helgaas
2019-06-26 1:07 ` Greg Kroah-Hartman
0 siblings, 1 reply; 3+ messages in thread
From: Bjorn Helgaas @ 2019-06-25 22:36 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Rafael J. Wysocki, Myron Stowe, linux-pci, linux-kernel
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);
}
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: mmap/munmap in sysfs
2019-06-25 22:36 mmap/munmap in sysfs Bjorn Helgaas
@ 2019-06-26 1:07 ` Greg Kroah-Hartman
2019-06-26 11:06 ` Rafael J. Wysocki
0 siblings, 1 reply; 3+ messages in thread
From: Greg Kroah-Hartman @ 2019-06-26 1:07 UTC (permalink / raw)
To: Bjorn Helgaas, Rafael J. Wysocki; +Cc: Myron Stowe, linux-pci, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mmap/munmap in sysfs
2019-06-26 1:07 ` Greg Kroah-Hartman
@ 2019-06-26 11:06 ` Rafael J. Wysocki
0 siblings, 0 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2019-06-26 11:06 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Bjorn Helgaas, Myron Stowe, linux-pci, linux-kernel, Mika Westerberg
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.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-06-26 1:07 ` Greg Kroah-Hartman
2019-06-26 11:06 ` Rafael J. Wysocki
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