On 21/07/28 01:13PM, Bjorn Helgaas wrote:
> On Wed, Jul 28, 2021 at 11:29:50PM +0530, Amey Narkhede wrote:
> > On 21/07/27 06:28PM, Bjorn Helgaas wrote:
> > > On Fri, Jul 09, 2021 at 06:08:09PM +0530, Amey Narkhede wrote:
> > > > Add reset_method sysfs attribute to enable user to query and set user
> > > > preferred device reset methods and their ordering.
> > > >
> > > > Co-developed-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > > > Signed-off-by: Amey Narkhede <ameynarkhede03@xxxxxxxxx>
> > > > ---
> > > > Documentation/ABI/testing/sysfs-bus-pci | 19 +++++
> > > > drivers/pci/pci-sysfs.c | 103 ++++++++++++++++++++++++
> > > > 2 files changed, 122 insertions(+)
> > > >
> > > > diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> > > > index ef00fada2..43f4e33c7 100644
> > > > --- a/Documentation/ABI/testing/sysfs-bus-pci
> > > > +++ b/Documentation/ABI/testing/sysfs-bus-pci
> > > > @@ -121,6 +121,25 @@ Description:
> > > > child buses, and re-discover devices removed earlier
> > > > from this part of the device tree.
> > > >
> > > > +What: /sys/bus/pci/devices/.../reset_method
> > > > +Date: March 2021
> > > > +Contact: Amey Narkhede <ameynarkhede03@xxxxxxxxx>
> > > > +Description:
> > > > + Some devices allow an individual function to be reset
> > > > + without affecting other functions in the same slot.
> > > > +
> > > > + For devices that have this support, a file named
> > > > + reset_method will be present in sysfs. Initially reading
> > > > + this file will give names of the device supported reset
> > > > + methods and their ordering. After write, this file will
> > > > + give names and ordering of currently enabled reset methods.
> > > > + Writing the name or comma separated list of names of any of
> > > > + the device supported reset methods to this file will set
> > > > + the reset methods and their ordering to be used when
> > > > + resetting the device. Writing empty string to this file
> > > > + will disable ability to reset the device and writing
> > > > + "default" will return to the original value.
> > > > +
> > > > What: /sys/bus/pci/devices/.../reset
> > > > Date: July 2009
> > > > Contact: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > >
> > [...]
> >
> > > > + int i;
> > > > +
> > > > + if (sysfs_streq(name, ""))
> > > > + continue;
> > > > +
> > > > + name = strim(name);
> > > > +
> > > > + for (i = 1; i < PCI_NUM_RESET_METHODS; i++) {
> > > > + if (sysfs_streq(name, pci_reset_fn_methods[i].name) &&
> > > > + !pci_reset_fn_methods[i].reset_fn(pdev, 1)) {
> > > > + reset_methods[n++] = i;
> > >
> > > Can we build this directly in pdev->reset_methods[] so we don't need
> > > the memcpy() below?
> > >
> > This is to avoid writing partial values directly to dev->reset_methods.
> > So for example if user writes flr,unsupported_value then
> > dev->reset_methods should not be modified even though flr is valid reset
> > method in this example to avoid partial writes. Either operation(in this
> > case writing supported reset methods to reset_method attr) succeeds
> > completely or it fails othewise.
>
> I guess the question is, if somebody writes
>
> flr junk bus
>
> and we set the supported methods to "flr bus", is that OK? It seems
> OK to me; obviously we have to protect ourselves from attack, but
> over-zealous checking can make things unnecessarily complicated.
The problem is once we encounter "junk" we return -EINVAL so in your
example we only set flr.
Thanks,
Amey
