linux-kernel - Re: [PATCH v3 3/3] PCI: Avoid slot reset for Cavium cn8xxx root ports

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170831100130.5c8a922e@w520.home>
Date:   Thu, 31 Aug 2017 10:01:30 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jan Glauber <jan.glauber@...iumnetworks.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, david.daney@...ium.com,
        Jon Masters <jcm@...hat.com>,
        Robert Richter <robert.richter@...ium.com>,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org
Subject: Re: [PATCH v3 3/3] PCI: Avoid slot reset for Cavium cn8xxx root
 ports

On Thu, 31 Aug 2017 11:40:52 +0200
Jan Glauber <jan.glauber@...iumnetworks.com> wrote:

> On Wed, Aug 30, 2017 at 08:40:12AM -0600, Alex Williamson wrote:
> > On Wed, 30 Aug 2017 16:24:54 +0200
> > Jan Glauber <jglauber@...ium.com> wrote:
> >   
> > > Root ports of cn8xxx do not function after a slot reset when used with
> > > some e1000e and LSI HBA devices. Add a quirk to prevent slot reset on
> > > these root ports.
> > > 
> > > Signed-off-by: Jan Glauber <jglauber@...ium.com>
> > > ---
> > >  drivers/pci/quirks.c | 16 ++++++++++++++++
> > >  1 file changed, 16 insertions(+)
> > > 
> > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > > index 85191b8..6679971 100644
> > > --- a/drivers/pci/quirks.c
> > > +++ b/drivers/pci/quirks.c
> > > @@ -845,6 +845,22 @@ static void quirk_cavium_sriov_rnm_link(struct pci_dev *dev)
> > >  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_CAVIUM, 0xa018, quirk_cavium_sriov_rnm_link);
> > >  #endif
> > >  
> > > +/*
> > > + * Root port on some Cavium CN8xxx chips do not successfully complete
> > > + * a bus reset when used with certain types of child devices. Config
> > > + * space access to the child may quit responding. Flag all devices under
> > > + * the secondary bus as non-resettable.
> > > + */
> > > +static void quirk_CN8xxx_secondary_bus(struct pci_dev *dev)
> > > +{
> > > +	struct pci_dev *pdev;
> > > +
> > > +	dev_warn(&dev->dev, "Cavium CN8xxx quirk detected; reset for devices on secondary bus disabled\n");
> > > +	list_for_each_entry(pdev, &dev->subordinate->devices, bus_list)
> > > +		pdev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET;
> > > +}
> > > +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_CAVIUM, 0xa100, quirk_CN8xxx_secondary_bus);
> > > +
> > >  /*
> > >   * Some settings of MMRBC can lead to data corruption so block changes.
> > >   * See AMD 8131 HyperTransport PCI-X Tunnel Revision Guide  
> > 
> > 
> > This doesn't seem reliable, doesn't the user just need to remove and
> > reprobe the slot and the device would re-appear without this flag set?  
> 
> No, I tried before to disable the slot with "echo 0 > /sys/bus/pci/slots/3/power"
> but that does not work as it is not supported.
> 
> I'm not familiar with the quirk types, would another one be better
> suited here (even if we don't have the problem you descibed)?

The scenario I'm mentioning is to "echo 1 > /sys/bus/pci/devices/<some
device under the slot>/remove", then "echo <that device address> >
/sys/bus/pci/rescan".  This would break the ordering implicit in using
a fixup defined for the root port.  It seems like it'd make a lot more
sense to add a test on the parent bridge more similar to how the bus
reset works.  It's not the subordinate devices imposing the
no-bus-reset flag, it's the bridge device and the objects and code
should support and reflect that.  Thanks,

Alex