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Date: Wed, 28 Nov 2012 20:30:48 +0000
From: "Pandarathil, Vijaymohan R" <vijaymohan.pandarathil@...com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linasvepstas@...il.com" <linasvepstas@...il.com>,
Myron Stowe <myron.stowe@...il.com>,
"Ortiz, Lance E" <lance.oritz@...com>,
Huang Ying <ying.huang@...el.com>,
Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
"Patterson, Andrew D (LeftHand Networks)" <andrew.patterson@...com>,
"Zhang Yanmin" <yanmin.zhang@...el.com>
Subject: RE: [PATCH v3] PCI-AER: Do not report successful error recovery for
devices with AER-unaware drivers
Looks correct.
Vijay
> -----Original Message-----
> From: Bjorn Helgaas [mailto:bhelgaas@...gle.com]
> Sent: Wednesday, November 28, 2012 12:15 PM
> To: Pandarathil, Vijaymohan R
> Cc: linux-kernel@...r.kernel.org; linux-pci@...r.kernel.org;
> linasvepstas@...il.com; Myron Stowe; Ortiz, Lance E; Huang Ying; Hidetoshi
> Seto; Patterson, Andrew D (LeftHand Networks); Zhang Yanmin
> Subject: Re: [PATCH v3] PCI-AER: Do not report successful error recovery
> for devices with AER-unaware drivers
>
> On Sat, Nov 17, 2012 at 4:47 AM, Pandarathil, Vijaymohan R
> <vijaymohan.pandarathil@...com> wrote:
> > When an error is detected on a PCIe device which does not have an
> > AER-aware driver, prevent AER infrastructure from reporting
> > successful error recovery.
> >
> > This is because the report_error_detected() function that gets
> > called in the first phase of recovery process allows forward
> > progress even when the driver for the device does not have AER
> > capabilities. It seems that all callbacks (in pci_error_handlers
> > structure) registered by drivers that gets called during error
> > recovery are not mandatory. So the intention of the infrastructure
> > design seems to be to allow forward progress even when a specific
> > callback has not been registered by a driver. However, if error
> > handler structure itself has not been registered, it doesn't make
> > sense to allow forward progress.
> >
> > As a result of the current design, in the case of a single device
> > having an AER-unaware driver or in the case of any function in a
> > multi-function card having an AER-unaware driver, a successful
> > recovery is reported.
> >
> > Typical scenario this happens is when a PCI device is detached
> > from a KVM host and the pci-stub driver on the host claims the
> > device. The pci-stub driver does not have error handling capabilities
> > but the AER infrastructure still reports that the device recovered
> > successfully.
> >
> > The changes proposed here leaves the device(s)in an unrecovered state
> > if the driver for the device or for any device in the subtree
> > does not have error handler structure registered. This reflects
> > the true state of the device and prevents any partial recovery (or no
> > recovery at all) reported as successful.
> >
> >
> > v3:
> > - Fixed a checkpatch/build issue
> >
> > v2:
> > - Made changes so that all devices in the subtree have the error
> > state set correctly.
> >
> >
> > Reviewed-by: Linas Vepstas <linasvepstas <at> gmail.com>
> > Reviewed-by: Myron Stowe <mstowe <at> redhat.com>
> > Reviewed-by: Bjorn Helgaas <bhelgaas <at> google.com>
> > Signed-off-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@...com>
>
> I added this to my -next branch, which will be merged for v3.8.
>
> Please double-check that I resolved the merge conflict correctly. It
> should show up here in the next few minutes:
>
> http://git.kernel.org/?p=linux/kernel/git/helgaas/pci.git;a=shortlog;h=refs
> /heads/next
>
> > drivers/pci/pcie/aer/aerdrv.h | 5 ++++-
> > drivers/pci/pcie/aer/aerdrv_core.c | 21 ++++++++++++++++++---
> > include/linux/pci.h | 3 +++
> > 3 files changed, 25 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/aer/aerdrv.h
> b/drivers/pci/pcie/aer/aerdrv.h
> > index 94a7598..22f840f 100644
> > --- a/drivers/pci/pcie/aer/aerdrv.h
> > +++ b/drivers/pci/pcie/aer/aerdrv.h
> > @@ -87,6 +87,9 @@ struct aer_broadcast_data {
> > static inline pci_ers_result_t merge_result(enum pci_ers_result orig,
> > enum pci_ers_result new)
> > {
> > + if (new == PCI_ERS_RESULT_NO_AER_DRIVER)
> > + return PCI_ERS_RESULT_NO_AER_DRIVER;
> > +
> > if (new == PCI_ERS_RESULT_NONE)
> > return orig;
> >
> > @@ -97,7 +100,7 @@ static inline pci_ers_result_t merge_result(enum
> pci_ers_result orig,
> > break;
> > case PCI_ERS_RESULT_DISCONNECT:
> > if (new == PCI_ERS_RESULT_NEED_RESET)
> > - orig = new;
> > + orig = PCI_ERS_RESULT_NEED_RESET;
> > break;
> > default:
> > break;
> > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c
> b/drivers/pci/pcie/aer/aerdrv_core.c
> > index 9f80cb0..b67f91a 100644
> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
> > @@ -232,11 +232,26 @@ static int report_error_detected(struct pci_dev
> *dev, void *data)
> > dev->driver ?
> > "no AER-aware driver" : "no driver");
> > }
> > - return 0;
> > +
> > + /*
> > + * If there's any device in the subtree that does not
> > + * have an error_detected callback, returning
> > + * PCI_ERS_RESULT_NO_AER_DRIVER prevents calling of
> > + * the subsequent mmio_enabled/slot_reset/resume
> > + * callbacks of "any" device in the subtree. All the
> > + * devices in the subtree are left in the error state
> > + * without recovery.
> > + */
> > +
> > + if (!(dev->hdr_type & PCI_HEADER_TYPE_BRIDGE))
> > + vote = PCI_ERS_RESULT_NO_AER_DRIVER;
> > + else
> > + vote = PCI_ERS_RESULT_NONE;
> > + } else {
> > + err_handler = dev->driver->err_handler;
> > + vote = err_handler->error_detected(dev, result_data-
> >state);
> > }
> >
> > - err_handler = dev->driver->err_handler;
> > - vote = err_handler->error_detected(dev, result_data->state);
> > result_data->result = merge_result(result_data->result, vote);
> > return 0;
> > }
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index ab17a08..c458602 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -540,6 +540,9 @@ enum pci_ers_result {
> >
> > /* Device driver is fully recovered and operational */
> > PCI_ERS_RESULT_RECOVERED = (__force pci_ers_result_t) 5,
> > +
> > + /* No AER capabilities registered for the driver */
> > + PCI_ERS_RESULT_NO_AER_DRIVER = (__force pci_ers_result_t) 6,
> > };
> >
> > /* PCI bus error event callbacks */
> > --
> > 1.7.11.3
> >
--
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