Re: [PATCH v2 1/1] powerpc/pseries: fix EEH recovery of some IOV devices

[Sam Bobroff <sbobroff@linux.ibm.com>]

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On Mon, Jul 02, 2018 at 10:59:24AM +1000, Michael Ellerman wrote:
> Sam Bobroff <sbobroff@linux.ibm.com> writes:
> 
> > EEH recovery currently fails on pSeries for some IOV capable PCI
> > devices, if CONFIG_PCI_IOV is on and the hypervisor doesn't provide
> > certain device tree properties for the device. (Found on an IOV
> > capable device using the ipr driver.)
> >
> > Recovery fails in pci_enable_resources() at the check on r->parent,
> > because r->flags is set and r->parent is not.  This state is due to
> > sriov_init() setting the start, end and flags members of the IOV BARs
> > but the parent not being set later in
> > pseries_pci_fixup_iov_resources(), because the
> > "ibm,open-sriov-vf-bar-info" property is missing.
> >
> > Correct this by zeroing the resource flags for IOV BARs when they
> > can't be configured.
> >
> > Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
> > ---
> > Hi,
> >
> > This is a fix to allow EEH recovery to succeed in a specific situation,
> > which I've tried to explain in the commit message.
> >
> > As with the RFC version, the IOV BARs are disabled by setting the resource
> > flags to 0 but the other fields are now left as-is because that is what is done
> > elsewhere (see sriov_init() and __pci_read_base()).
> >
> > I've also examined the concern raised by Bjorn Helgaas, that VFs could be
> > enabled later after the BARs are disabled, and it already seems safe: enabling
> > VFs (on pseries) depends on another device tree property,
> > "ibm,number-of-configurable-vfs" as well as support for the RTAS function
> > "ibm_map_pes". Since these are all part of the hypervisor's support for IOV it
> > seems unlikely that we would ever see some of them but not all. (None are
> > currently provided by QEMU/KVM.) (Additionally, the ipr driver on which the EEH
> > recovery failure was discovered doesn't even seem to have SR-IOV support so it
> > certainly can't enable VFs.)
> 
> Can you fold/reword the above into the change log, it seems like useful
> detail.
> 
> cheers

Sure, sounds good.


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