On 2018-07-18 03:06, Bjorn Helgaas wrote:
On Tue, Jul 17, 2018 at 02:03:29PM -0500, Bjorn Helgaas wrote:
Hi Oza,
Thanks for doing this!
On Fri, Jun 22, 2018 at 05:58:09AM -0400, Oza Pawandeep wrote:
> pci_cleanup_aer_uncorrect_error_status() is called by different slot_reset
> callbacks in case of ERR_NONFATAL.
IIRC, the current strategy is:
ERR_COR: log only
ERR_NONFATAL: call driver callbacks (pci_error_handlers)
ERR_FATAL: remove device and re-enumerate
So these slot_reset callbacks are only used for ERR_NONFATAL, which
are all uncorrectable errors, of course.
This patch makes it so that when the slot_reset callbacks call
pci_cleanup_aer_uncorrect_error_status(), we only clear the
bits set by ERR_NONFATAL events (this is determined by
PCI_ERR_UNCOR_SEVER).
That makes good sense to me. All these status bits are RW1CS, so they
will be preserved across a reset but will be cleared when we
re-enumerate, in this path:
pci_init_capabilities
pci_aer_init
pci_cleanup_aer_error_status_regs
# clear all PCI_ERR_UNCOR_STATUS and PCI_ERR_COR_STATUS bits
> AER uncorrectable error status should take severity into account in order
> to clear the bits, so that ERR_NONFATAL path does not clear the bit which
> are marked with severity fatal.
Two comments:
1) Can you split this into two patches, one that changes
pci_cleanup_aer_uncorrect_error_status() so it looks like the error
clearing code in aer_error_resume(), and a second that factors out the
duplicate code?
2) Maybe use "sev" or "sever" instead of "mask" for the local
variable, since there is also a separate PCI_ERR_UNCOR_MASK register,
which is not involved here.
Let me back up a little here: I'm not asking you to do the things
below here. They're just possible future things, so we can think
about them after this series. And the things above are things I can
easily do myself. So no action required from you, unless you think
I'm on the wrong track :)
I agree with your points, and have taken them into account for future
series reference as well.
what about PATCH-2 of this series ?
that clears ERR_FATAL bits, but as you said, during re-enumeration
pci_init_capabilities
pci_aer_init
pci_cleanup_aer_error_status_regs
# clear all PCI_ERR_UNCOR_STATUS and PCI_ERR_COR_STATUS bits
but that should clear the ERR_FATAL of the devices beneath.
PATCH2: we are doing it for BRIDGE where we think where ERR_FATAL was
reported by bridge and the problem is with downstream link.
if ((service == PCIE_PORT_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_cleanup_aer_uncorrect_error_status(dev);
}
so overall, I think all the patches are required, if you have comments
please let me know.
so far I see that, no action is required from me.
3) The "pci_cleanup_aer_uncorrect_error_status()" name no longer
really describes what this does. Something like
"pci_aer_clear_nonfatal_status()" would be more descriptive. But I
see you have a subsequent patch (which I haven't looked at yet) that
is related to this.
4) I don't think the driver slot_reset callbacks should be responsible
for clearing these AER status bits. Can we clear them somewhere in
the pcie_do_nonfatal_recovery() path and remove these calls from the
drivers?
5) In principle, we should only read PCI_ERR_UNCOR_STATUS *once* per
device when handling an error. We currently read it three times:
aer_isr
aer_isr_one_error
find_source_device
find_device_iter
is_error_source
read PCI_ERR_UNCOR_STATUS # 1
aer_process_err_devices
get_device_error_info(e_info->dev[i])
read PCI_ERR_UNCOR_STATUS # 2
handle_error_source
pcie_do_nonfatal_recovery
...
report_slot_reset
driver->err_handler->slot_reset
pci_cleanup_aer_uncorrect_error_status
read PCI_ERR_UNCOR_STATUS # 3
OK, that was more than two comments :)
