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Message-ID: <20180508235330.GN161390@bhelgaas-glaptop.roam.corp.google.com>
Date: Tue, 8 May 2018 18:53:30 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Oza Pawandeep <poza@...eaurora.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Philippe Ombredanne <pombredanne@...b.com>,
Thomas Gleixner <tglx@...utronix.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Kate Stewart <kstewart@...uxfoundation.org>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
Dongdong Liu <liudongdong3@...wei.com>,
Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
Sinan Kaya <okaya@...eaurora.org>,
Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v15 3/9] PCI/AER: Handle ERR_FATAL with removal and
re-enumeration of devices
On Thu, May 03, 2018 at 01:03:52AM -0400, Oza Pawandeep wrote:
> This patch alters the behavior of handling of ERR_FATAL, where removal
> of devices is initiated, followed by reset link, followed by
> re-enumeration.
>
> So the errors are handled in a different way as follows:
> ERR_NONFATAL => call driver recovery entry points
> ERR_FATAL => remove and re-enumerate
>
> please refer to Documentation/PCI/pci-error-recovery.txt for more details.
>
> Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
>
> diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c
> index 779b387..206f590 100644
> --- a/drivers/pci/pcie/aer/aerdrv.c
> +++ b/drivers/pci/pcie/aer/aerdrv.c
> @@ -330,6 +330,13 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
> reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
> pci_write_config_dword(dev, pos + PCI_ERR_ROOT_COMMAND, reg32);
>
> + /*
> + * This function is called only on ERR_FATAL now, and since
> + * the pci_report_resume is called only in ERR_NONFATAL case,
> + * the clearing part has to be taken care here.
> + */
> + aer_error_resume(dev);
I don't understand this part. Previously the ERR_FATAL path looked like
this:
do_recovery
reset_link
driver->reset_link
aer_root_reset
pci_reset_bridge_secondary_bus # <-- reset
broadcast_error_message(..., report_resume)
pci_walk_bus(..., report_resume, ...)
report_resume
if (cb == report_resume)
pci_cleanup_aer_uncorrect_error_status
pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # <-- clear status
After this patch, it will look like this:
do_recovery
do_fatal_recovery
pci_cleanup_aer_uncorrect_error_status
pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # <-- clear status
reset_link
driver->reset_link
aer_root_reset
pci_reset_bridge_secondary_bus # <-- reset
aer_error_resume
pcie_capability_write_word(PCI_EXP_DEVSTA) # <-- clear more
pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # <-- clear status
So if I'm understanding correctly, the new path clears the status too
early, then clears it again (plus clearing DEVSTA, which we didn't do
before) later.
I would think we would want to leave aer_root_reset() alone, and just move
the pci_cleanup_aer_uncorrect_error_status() in do_fatal_recovery() down so
it happens after we call reset_link(). That way the reset/clear sequence
would be the same as it was before.
> return PCI_ERS_RESULT_RECOVERED;
> }
>
> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
> index 0ea5acc..655d4e8 100644
> --- a/drivers/pci/pcie/aer/aerdrv_core.c
> +++ b/drivers/pci/pcie/aer/aerdrv_core.c
> @@ -20,6 +20,7 @@
> #include <linux/slab.h>
> #include <linux/kfifo.h>
> #include "aerdrv.h"
> +#include "../../pci.h"
>
> #define PCI_EXP_AER_FLAGS (PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | \
> PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
> @@ -474,6 +475,44 @@ static pci_ers_result_t reset_link(struct pci_dev *dev)
> return status;
> }
>
> +static pci_ers_result_t do_fatal_recovery(struct pci_dev *dev, int severity)
> +{
> + struct pci_dev *udev;
> + struct pci_bus *parent;
> + struct pci_dev *pdev, *temp;
> + pci_ers_result_t result = PCI_ERS_RESULT_RECOVERED;
> +
> + if (severity == AER_FATAL)
> + pci_cleanup_aer_uncorrect_error_status(dev);
> +
> + if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
> + udev = dev;
> + else
> + udev = dev->bus->self;
> +
> + parent = udev->subordinate;
> + pci_lock_rescan_remove();
> + list_for_each_entry_safe_reverse(pdev, temp, &parent->devices,
> + bus_list) {
> + pci_dev_get(pdev);
> + pci_dev_set_disconnected(pdev, NULL);
> + if (pci_has_subordinate(pdev))
> + pci_walk_bus(pdev->subordinate,
> + pci_dev_set_disconnected, NULL);
> + pci_stop_and_remove_bus_device(pdev);
> + pci_dev_put(pdev);
> + }
> +
> + result = reset_link(udev);
> + if (result == PCI_ERS_RESULT_RECOVERED)
> + if (pcie_wait_for_link(udev, true))
> + pci_rescan_bus(udev->bus);
> +
> + pci_unlock_rescan_remove();
> +
> + return result;
> +}
> +
> /**
> * do_recovery - handle nonfatal/fatal error recovery process
> * @dev: pointer to a pci_dev data structure of agent detecting an error
> @@ -485,11 +524,15 @@ static pci_ers_result_t reset_link(struct pci_dev *dev)
> */
> static void do_recovery(struct pci_dev *dev, int severity)
> {
> - pci_ers_result_t status, result = PCI_ERS_RESULT_RECOVERED;
> + pci_ers_result_t status;
> enum pci_channel_state state;
>
> - if (severity == AER_FATAL)
> - state = pci_channel_io_frozen;
> + if (severity == AER_FATAL) {
> + status = do_fatal_recovery(dev, severity);
> + if (status != PCI_ERS_RESULT_RECOVERED)
> + goto failed;
> + return;
> + }
> else
> state = pci_channel_io_normal;
>
> @@ -498,12 +541,6 @@ static void do_recovery(struct pci_dev *dev, int severity)
> "error_detected",
> report_error_detected);
>
> - if (severity == AER_FATAL) {
> - result = reset_link(dev);
> - if (result != PCI_ERS_RESULT_RECOVERED)
> - goto failed;
> - }
> -
> if (status == PCI_ERS_RESULT_CAN_RECOVER)
> status = broadcast_error_message(dev,
> state,
> --
> 2.7.4
>
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