From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
Myron Stowe <myron.stowe@redhat.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: Re: mmap/munmap in sysfs
Date: Wed, 26 Jun 2019 13:06:52 +0200 [thread overview]
Message-ID: <2001283.OsK9664mvh@kreacher> (raw)
In-Reply-To: <20190626010746.GA22454@kroah.com>
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.
prev parent reply other threads:[~2019-06-26 11:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
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