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

From: poza
Date: Wed May 16 2018 - 03:44:35 EST

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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".

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.

Next message: Lee Jones: "[GIT PULL] Immutable branch between MFD and PWM due for the v4.18 merge window"
Previous message: Peter Zijlstra: "Re: [PATCH] Makefile: disable PIE before testing asm goto"
Next in thread: Bjorn Helgaas: "Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC"
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