On Fri, 2013-12-13 at 15:35 -0700, Bjorn Helgaas wrote:
> On Fri, Dec 13, 2013 at 8:41 AM, Betty Dall <betty.dall@xxxxxx> wrote:
> > There are three functions exported from aerdrv_core.c that could be
> > called when the system is in firmware first mode:
> > pci_enable_pcie_error_reporting(), pci_disable_pcie_error_reporting, and
> > pci_cleanup_aer_uncorrect_error_status(). The first two functions check if
> > we are in firmware first mode and return immediately.
> > pci_cleanup_aer_uncorrect_error_status() does not check firmware first
> > mode. The problem is that all of these functions should not access the AER
> > registers in firmware first mode because the firmware has not granted OS
> > control of the AER registers through the _OSC.
>
> This looks like a good fix to me. If I read aer_acpi_firmware_first()
> correctly, we don't even *ask* for control of AER if
> ACPI_HEST_FIRMWARE_FIRST appears anywhere in the HEST. Does that
> match your understanding?
Yes, when the system is in firmware first mode the code setting the _OSC
control register does not ask for AER control.
>
> > Many drivers call this
> > function in their pci_error_handlers in firmware first mode.
>
> Drivers don't have any idea whether their device is in firmware-first
> mode, do they?
Right. And I think we want to keep it that way. Having this function is
a good thing so that the firmware first can be abstracted from the
drivers.
>
> > The fix is to change pci_cleanup_aer_uncorrect_error_status() to check
> > firmware first mode before accessing the AER registers. If it is in firmware
> > first mode, return 0. I considered returning -EIO, but decided the status
> > has been cleaned up appropriately for firmware first. Returning 0 also avoids
> > an error message. Not many places check the return of this function, and the
> > ones that do, print an error message and continue such as:
> > err = pci_cleanup_aer_uncorrect_error_status(pdev);
> > if (err) {
> > dev_err(&pdev->dev,
> > "pci_cleanup_aer_uncorrect_error_status failed 0x%0x\n",
> > err); /* non-fatal, continue */
> > }
> > That error message is how I found this problem, and it is not applicable
> > for the firmware first recovery path.
>
> I'm curious -- did you find this problem because you saw a message
> when pci_cleanup_aer_uncorrect_error_status() returned failure? The
> only way it can return failure is if there is no AER capability, and
> that should be completely independent of whether we're in
> firmware-first mode.
Yes, I saw the error message during error injection testing and using a
firmware that denies access to AER control because it is firmware first.
You are right that it would only print out when there is no AER
capability. I was reading code looking for places that might access the
AER registers in firmware first mode. This is the only one I found.
-Betty
>
> > Signed-off-by: Betty Dall <betty.dall@xxxxxx>
> > ---
> >
> > drivers/pci/pcie/aer/aerdrv_core.c | 3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> >
> > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
> > index b2c8881..1f60408 100644
> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
> > @@ -62,6 +62,9 @@ int pci_cleanup_aer_uncorrect_error_status(struct pci_dev *dev)
> > int pos;
> > u32 status;
> >
> > + if (pcie_aer_get_firmware_first(dev))
> > + return 0;
> > +
> > pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
> > if (!pos)
> > return -EIO;
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