On Wed, Feb 24, 2016 at 05:48:33AM +0800, Hannes Reinecke wrote: > On 02/23/2016 10:07 PM, Bjorn Helgaas wrote: > > Hi Hannes, > > > > Thanks for taking a look at the rest of these. > > > > On Mon, Feb 22, 2016 at 06:46:23PM -0600, Bjorn Helgaas wrote: > >> Hi Hannes, > >> > >> This is a revision of your v3 series: > >> http://lkml.kernel.org/r/1455525722-122040-1-git-send-email-hare@xxxxxxx > >> > >> Here's the description from your v3 posting: > >> > >> the current PCI VPD page access assumes that the entire possible VPD > >> data is readable. However, the spec only guarantees a VPD data up to > >> the 'end' marker, with everything beyond that being undefined. > >> This causes a system lockup on certain devices. > >> > >> With this patch we always set the VPD sysfs attribute size to '0', and > >> calculate the available VPD size on the first access. > >> If no valid data can be read an I/O error is returned. > > > > Just to see if I have this right: the VPD file size in sysfs will > > always appear as zero, regardless of whether it has been read or > > written, right? I don't think the user-visible size should change. > > > That is correct. > As the actual size is evaluated on the first access, we don't have it > available when creating the sysfs attribute itself. > And when using the nominal size of 32k some bright program might try to > jump to somewhere in the middle of the data, which will make calculating > the validity of this horribly complex. > Setting it to '0' is an easy way of avoiding this kinda games. > > So yes, there will be a user-visible change, but it shouldn't affect the > programs accessing this attribute. > lspci works happily with these changes What is the user-visible change? Here's what I'm thinking. If we do this: ls -l /sys/.../vpd dd if=/sys/.../vpd bs=1 count=1 ls -l /sys/.../vpd Do we see different sizes from the two "ls" invocations? My thought is that we should see '0' both times, because I don't really think that output should change depending on previous actions of this user or other users. I though you were confirming that we do always see '0', but then you mentioned a user-visible change; is there a different change you're thinking of? Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
