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Message-ID: <CAErSpo7VvWreoTj7MUE3cMGaM1dVMfZymO=1P-m8E-joRSgE7g@mail.gmail.com>
Date: Wed, 28 Nov 2012 13:15:21 -0700
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: "Pandarathil, Vijaymohan R" <vijaymohan.pandarathil@...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
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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