From: Bjorn Helgaas <helgaas@kernel.org>
To: Hannes Reinecke <hare@suse.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org,
Jordan Hargrave <Jordan_Hargrave@dell.com>,
Babu Moger <babu.moger@oracle.com>,
Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [PATCH v4 00/11] PCI VPD access fixes
Date: Tue, 23 Feb 2016 16:36:11 -0600 [thread overview]
Message-ID: <20160223223611.GA6495@localhost> (raw)
In-Reply-To: <56CCD3B1.3060702@suse.de>
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@suse.de
> >>
> >> 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
next prev parent reply other threads:[~2016-02-23 22:36 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 0:46 [PATCH v4 00/11] PCI VPD access fixes Bjorn Helgaas
2016-02-23 0:46 ` [PATCH v4 01/11] PCI: Update VPD definitions Bjorn Helgaas
2016-02-23 0:46 ` [PATCH v4 02/11] PCI: Allow access to VPD attributes with size 0 Bjorn Helgaas
2016-02-23 0:46 ` [PATCH v4 03/11] PCI: Use bitfield instead of bool for struct pci_vpd_pci22.busy Bjorn Helgaas
2016-02-23 12:19 ` Hannes Reinecke
2016-02-23 0:46 ` [PATCH v4 04/11] PCI: Determine actual VPD size on first access Bjorn Helgaas
2016-02-23 0:47 ` [PATCH v4 05/11] FIXME need bugzilla link Bjorn Helgaas
2016-02-23 0:47 ` [PATCH v4 06/11] PCI: Move pci_read_vpd() and pci_write_vpd() close to other VPD code Bjorn Helgaas
2016-02-23 12:20 ` Hannes Reinecke
2016-02-23 0:47 ` [PATCH v4 07/11] PCI: Move pci_vpd_release() from header file to pci/access.c Bjorn Helgaas
2016-02-23 12:21 ` Hannes Reinecke
2016-02-23 0:47 ` [PATCH v4 08/11] PCI: Remove struct pci_vpd_ops.release function pointer Bjorn Helgaas
2016-02-23 12:22 ` Hannes Reinecke
2016-02-23 0:47 ` [PATCH v4 09/11] PCI: Rename VPD symbols to remove unnecessary "pci22" Bjorn Helgaas
2016-02-23 12:23 ` Hannes Reinecke
2016-02-23 0:47 ` [PATCH v4 10/11] PCI: Fold struct pci_vpd_pci22 into struct pci_vpd Bjorn Helgaas
2016-02-23 12:24 ` Hannes Reinecke
2016-02-23 0:47 ` [PATCH v4 11/11] PCI: Sleep rather than busy-wait for VPD access completion Bjorn Helgaas
2016-02-23 12:25 ` Hannes Reinecke
2016-02-23 14:07 ` [PATCH v4 00/11] PCI VPD access fixes Bjorn Helgaas
2016-02-23 21:48 ` Hannes Reinecke
2016-02-23 22:36 ` Bjorn Helgaas [this message]
2016-02-24 0:30 ` Hannes Reinecke
2016-02-24 0:45 ` Bjorn Helgaas
2016-02-23 17:11 ` Bjorn Helgaas
2016-02-24 4:52 ` Seymour, Shane M
2016-02-29 22:36 ` Babu Moger
2016-02-29 17:27 ` Babu Moger
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