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

From: poza
Date: Wed May 16 2018 - 07:43:24 EST

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In reply to: Bjorn Helgaas: "Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC"
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On 2018-05-16 16:22, Bjorn Helgaas wrote:

On Wed, May 16, 2018 at 01:46:25PM +0530, poza@xxxxxxxxxxxxxx wrote:

On 2018-05-16 05:26, Bjorn Helgaas wrote:
> On Fri, May 11, 2018 at 05:22:08PM +0530, poza@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
> > >
> > > 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".

Please still add a comment here about why the rescan behavior is
different.

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.

Oh, I missed this before. It makes sense to clear the AER status
here, but why do we need to call report_resume()? We just called all
the driver .remove() methods and detached the drivers from the
devices. So I don't think report_resume() will do anything
("dev->driver" should be NULL) except set the dev->error_state to
pci_channel_io_normal. We probably don't need that because we didn't
change error_state in this fatal error path.

if you remember, the path ends up calling
aer_error_resume

the existing code ends up calling aer_error_resume as follows.

do_recovery(pci_dev)
broadcast_error_message(..., error_detected, ...)
if (AER_FATAL)
reset_link(pci_dev)
udev = BRIDGE ? pci_dev : pci_dev->bus->self
driver->reset_link(udev)
aer_root_reset(udev)
if (CAN_RECOVER)
broadcast_error_message(..., mmio_enabled, ...)
if (NEED_RESET)
broadcast_error_message(..., slot_reset, ...)
broadcast_error_message(dev, ..., report_resume, ...)
if (BRIDGE)
report_resume
driver->resume
pcie_portdrv_err_resume
device_for_each_child(..., resume_iter)
resume_iter
driver->error_resume
aer_error_resume
pci_cleanup_aer_uncorrect_error_status(pci_dev) # only if BRIDGE
pci_write_config_dword(PCI_ERR_UNCOR_STATUS)

hence I think we have to call it in order to clear the root port PCI_ERR_UNCOR_STATUS and PCI_EXP_DEVSTA.
makes sense ?

Regards,
Oza.

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

Sorry, I must have forgotten to push it. It's there now at

https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/oza-v16

I don't know anything about the googlesource mirror, so I don't know
when it will get there.

Next message: Jason Wang: "Re: [RFC v4 4/5] virtio_ring: add event idx support in packed ring"
Previous message: Rafael J. Wysocki: "[PATCH 0/2] ACPI / PM: Dispatch EC GPE early on s2idle resume if LPS0 _DSM is used"
In reply to: Bjorn Helgaas: "Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC"
Next in thread: Bjorn Helgaas: "Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC"
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