Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC

poza
2018-05-16T08:16:25Z

On 2018-05-16 05:26, Bjorn Helgaas wrote:
> On Fri, May 11, 2018 at 05:22:08PM +0530, poza@codeaurora.org wrote:
>> On 2018-05-11 16:13, Oza Pawandeep wrote:
>> > DPC driver implements link_reset callback, and calls
>> > pci_do_fatal_recovery().
>> >
>> > Which follows standard path of ERR_FATAL recovery.
>> >
>> > Signed-off-by: Oza Pawandeep <poza@codeaurora.org>
>> >
>> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> > index 5e8857a..6af7595 100644
>> > --- a/drivers/pci/pci.h
>> > +++ b/drivers/pci/pci.h
>> > @@ -354,7 +354,7 @@ static inline resource_size_t
>> > pci_resource_alignment(struct pci_dev *dev,
>> > void pci_enable_acs(struct pci_dev *dev);
>> >
>> > /* PCI error reporting and recovery */
>> > -void pcie_do_fatal_recovery(struct pci_dev *dev);
>> > +void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service);
>> > void pcie_do_nonfatal_recovery(struct pci_dev *dev);
>> >
>> > bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
>> > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c
>> > b/drivers/pci/pcie/aer/aerdrv_core.c
>> > index fdfc474..36e622d 100644
>> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
>> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
>> > @@ -254,7 +254,7 @@ static void handle_error_source(struct pcie_device
>> > *aerdev,
>> > } else if (info->severity == AER_NONFATAL)
>> > pcie_do_nonfatal_recovery(dev);
>> > else if (info->severity == AER_FATAL)
>> > - pcie_do_fatal_recovery(dev);
>> > + pcie_do_fatal_recovery(dev, PCIE_PORT_SERVICE_AER);
>> > }
>> >
>> > #ifdef CONFIG_ACPI_APEI_PCIEAER
>> > @@ -321,7 +321,7 @@ static void aer_recover_work_func(struct work_struct
>> > *work)
>> > if (entry.severity == AER_NONFATAL)
>> > pcie_do_nonfatal_recovery(pdev);
>> > else if (entry.severity == AER_FATAL)
>> > - pcie_do_fatal_recovery(pdev);
>> > + pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_AER);
>> > pci_dev_put(pdev);
>> > }
>> > }
>> > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
>> > index 80ec384..5680c13 100644
>> > --- a/drivers/pci/pcie/dpc.c
>> > +++ b/drivers/pci/pcie/dpc.c
>> > @@ -73,29 +73,31 @@ static void dpc_wait_link_inactive(struct dpc_dev
>> > *dpc)
>> > pcie_wait_for_link(pdev, false);
>> > }
>> >
>> > -static void dpc_work(struct work_struct *work)
>> > +static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
>> > {
>> > - struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
>> > - struct pci_dev *dev, *temp, *pdev = dpc->dev->port;
>> > - struct pci_bus *parent = pdev->subordinate;
>> > - u16 cap = dpc->cap_pos, ctl;
>> > -
>> > - pci_lock_rescan_remove();
>> > - list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
>> > - bus_list) {
>> > - pci_dev_get(dev);
>> > - pci_dev_set_disconnected(dev, NULL);
>> > - if (pci_has_subordinate(dev))
>> > - pci_walk_bus(dev->subordinate,
>> > - pci_dev_set_disconnected, NULL);
>> > - pci_stop_and_remove_bus_device(dev);
>> > - pci_dev_put(dev);
>> > - }
>> > - pci_unlock_rescan_remove();
>> > -
>> > + struct dpc_dev *dpc;
>> > + struct pcie_device *pciedev;
>> > + struct device *devdpc;
>> > + u16 cap, ctl;
>> > +
>> > + /*
>> > + * DPC disables the Link automatically in hardware, so it has
>> > + * already been reset by the time we get here.
>> > + */
>> > +
>> > + devdpc = pcie_port_find_device(pdev, PCIE_PORT_SERVICE_DPC);
>> > + pciedev = to_pcie_device(devdpc);
>> > + dpc = get_service_data(pciedev);
>> > + cap = dpc->cap_pos;
>> > +
>> > + /*
>> > + * Waiting until the link is inactive, then clearing DPC
>> > + * trigger status to allow the port to leave DPC.
>> > + */
>> > dpc_wait_link_inactive(dpc);
>> > +
>> > if (dpc->rp_extensions && dpc_wait_rp_inactive(dpc))
>> > - return;
>> > + return PCI_ERS_RESULT_DISCONNECT;
>> > if (dpc->rp_extensions && dpc->rp_pio_status) {
>> > pci_write_config_dword(pdev, cap + PCI_EXP_DPC_RP_PIO_STATUS,
>> > dpc->rp_pio_status);
>> > @@ -108,6 +110,17 @@ static void dpc_work(struct work_struct *work)
>> > pci_read_config_word(pdev, cap + PCI_EXP_DPC_CTL, &ctl);
>> > pci_write_config_word(pdev, cap + PCI_EXP_DPC_CTL,
>> > ctl | PCI_EXP_DPC_CTL_INT_EN);
>> > +
>> > + return PCI_ERS_RESULT_RECOVERED;
>> > +}
>> > +
>> > +static void dpc_work(struct work_struct *work)
>> > +{
>> > + struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
>> > + struct pci_dev *pdev = dpc->dev->port;
>> > +
>> > + /* From DPC point of view error is always FATAL. */
>> > + pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_DPC);
>> > }
>> >
>> > static void dpc_process_rp_pio_error(struct dpc_dev *dpc)
>> > @@ -288,6 +301,7 @@ static struct pcie_port_service_driver dpcdriver = {
>> > .service = PCIE_PORT_SERVICE_DPC,
>> > .probe = dpc_probe,
>> > .remove = dpc_remove,
>> > + .reset_link = dpc_reset_link,
>> > };
>> >
>> > static int __init dpc_service_init(void)
>> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> > index 33a16b1..29ff148 100644
>> > --- a/drivers/pci/pcie/err.c
>> > +++ b/drivers/pci/pcie/err.c
>> > @@ -185,7 +185,7 @@ static pci_ers_result_t default_reset_link(struct
>> > pci_dev *dev)
>> > return PCI_ERS_RESULT_RECOVERED;
>> > }
>> >
>> > -static pci_ers_result_t reset_link(struct pci_dev *dev)
>> > +static pci_ers_result_t reset_link(struct pci_dev *dev, u32 service)
>> > {
>> > struct pci_dev *udev;
>> > pci_ers_result_t status;
>> > @@ -200,7 +200,7 @@ static pci_ers_result_t reset_link(struct pci_dev
>> > *dev)
>> > }
>> >
>> > /* Use the aer driver of the component firstly */
>> > - driver = pcie_port_find_service(udev, PCIE_PORT_SERVICE_AER);
>> > + driver = pcie_port_find_service(udev, service);
>> >
>> > if (driver && driver->reset_link) {
>> > status = driver->reset_link(udev);
>> > @@ -287,7 +287,7 @@ static pci_ers_result_t
>> > broadcast_error_message(struct pci_dev *dev,
>> > * followed by re-enumeration of devices.
>> > */
>> >
>> > -void pcie_do_fatal_recovery(struct pci_dev *dev)
>> > +void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service)
>> > {
>> > struct pci_dev *udev;
>> > struct pci_bus *parent;
>> > @@ -313,7 +313,7 @@ void pcie_do_fatal_recovery(struct pci_dev *dev)
>> > pci_dev_put(pdev);
>> > }
>> >
>> > - result = reset_link(udev);
>> > + result = reset_link(udev, service);
>> >
>> > if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>> > /*
>> > diff --git a/include/linux/aer.h b/include/linux/aer.h
>> > index 8f87bbe..0c506fe 100644
>> > --- a/include/linux/aer.h
>> > +++ b/include/linux/aer.h
>> > @@ -14,6 +14,7 @@
>> > #define AER_NONFATAL 0
>> > #define AER_FATAL 1
>> > #define AER_CORRECTABLE 2
>> > +#define DPC_FATAL 4
>
> I think DPC_FATAL can be 3, since these values are not used as a bit
> mask.
>
>> > struct pci_dev;
>>
>>
>> Hi Bjorn,
>>
>>
>> I have addressed all the comments, and I hope we are heading towards
>> closure.
>>
>> I just figure that pcie_do_fatal_recovery (which is getting executed
>> for
>> DPC as well)
>>
>> if (result == PCI_ERS_RESULT_RECOVERED) {
>> if (pcie_wait_for_link(udev, true))
>> pci_rescan_bus(udev->bus);
>> pci_info(dev, "Device recovery successful\n");
>> }
>>
>> I have to correct it to
>>
>> if (service==AER && result == PCI_ERS_RESULT_RECOVERED) {
>> if (pcie_wait_for_link(udev, true))
>> pci_rescan_bus(udev->bus);
>> pci_info(dev, "Device recovery successful\n");
>> }
>
> This patch is mostly a restructuring of DPC and doesn't really change
> its
> behavior. DPC didn't previously call pcie_wait_for_link() or
> pci_rescan_bus(), so I agree that adding the "service==AER" test will
> help preserve the existing DPC behavior.
>
> However, the rescan should happen with DPC *somewhere* and we should
> clarify where that is. Maybe for now we only need a comment about
> where
> that happens. Ideally, we could eventually converge this so the same
> mechanism is used for AER and DPC, so we wouldn't need a test like
> "service=AER".
>
>> rest of the things look okay to me.
>> If you have any more comments,
>> I can fix them with this one and hopefully v17 will be the final one.

I am sorry I pasted the wrong snippet.
following needs to be fixed in v17.
from:
if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
/*
* If the error is reported by a bridge, we think this
error
* is related to the downstream link of the bridge, so
we
* do error recovery on all subordinates of the bridge
instead
* of the bridge and clear the error status of the
bridge.
*/
pci_walk_bus(dev->subordinate, report_resume,
&result_data);
pci_cleanup_aer_uncorrect_error_status(dev);
}

to

if (service==AER && dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
/*
* If the error is reported by a bridge, we think this
error
* is related to the downstream link of the bridge, so
we
* do error recovery on all subordinates of the bridge
instead
* of the bridge and clear the error status of the
bridge.
*/
pci_walk_bus(dev->subordinate, report_resume,
&result_data);
pci_cleanup_aer_uncorrect_error_status(dev);
}

this is only needed in case of AER.

by the way I can not find pci/oza-v16 branch when I cloned
git clone
https://kernel.googlesource.com/pub/scm/linux/kernel/git/helgaas/pci

Regards,
Oza.

>>
>>
>> PS: I am going though the code more, and we can have some follow up
>> patches
>> (probably some cleanup)
>> for e.g. pcie_portdrv_slot_reset() checks
>> if (dev->error_state == pci_channel_io_frozen) {
>> dev->state_saved = true;
>> pci_restore_state(dev);
>> pcie_portdrv_restore_config(dev);
>> pci_enable_pcie_error_reporting(dev);
>> }
>>
>>
>> but now since the ERR_FATAL path does not call pcie_portdrv_slot_reset
>> the
>> check is meaning less.
>>
>> besides driver's shut_down callbacks might want to handle
>> pci_channel_io_frozen, but that something left to be discussed later.
>> So, I am not touching dev->error_state anywhere as of now in ERR_FATAL
>> case.
>>
>> Regards,
>> Oza.
>>
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