Re: [PATCH 1/2] PCI/AER: Do not reset the device status if doing firmware first handling.

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Hi,

On 6/17/20 2:31 AM, Jonathan Cameron wrote:
On Tue, 16 Jun 2020 11:00:32 -0700
"Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:

Hi Jonathan,

On 6/16/20 10:47 AM, Bjorn Helgaas wrote:
[+cc Sathy]

On Fri, May 22, 2020 at 01:31:33AM +0800, Jonathan Cameron wrote:
pci_aer_clear_device_status() currently resets the device status even when
firmware first handling is going on.  In particular it resets it on the
root port.

This has been discussed previously
https://lore.kernel.org/patchwork/patch/427375/.
pci_aer_clear_device_status() is only used by handle_error_source(). And
I don't think handle_error_source() is called in FF mode. Can you
give more details on this issue ?

It's called in pcie_do_recovery

https://elixir.bootlin.com/linux/latest/source/drivers/pci/pcie/err.c#L200

Which is called from both handle_error_source and aer_recover_work_func.

indirectly called from ghes_handle_aer / ghes_do_proc

This particular flow will only happen (I think) on hardware reduced ACPI systems.
Ok. Makes sense.

Jonathan


I don't think this reference is really pertinent, is it?  That patch
to b2c8881da764 changes pci_cleanup_aer_uncorrect_error_status() so it
doesn't clear PCI_ERR_UNCOR_STATUS in "firmware-first" mode.

But your patch only affects PCI_EXP_DEVSTA, not PCI_ERR_UNCOR_STATUS.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
   drivers/pci/pcie/aer.c | 3 +++
   1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index f4274d301235..43e78b97ace6 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -373,6 +373,9 @@ void pci_aer_clear_device_status(struct pci_dev *dev)
   {
   	u16 sta;
+ if (pcie_aer_get_firmware_first(dev))
use if (!pcie_aer_is_native(dev))
+		return;

This needs to be adjusted because pcie_aer_get_firmware_first() no
longer exists after 708b20003624 ("PCI/AER: Remove HEST/FIRMWARE_FIRST
parsing for AER ownership").

This will use the _OSC AER ownership bit to gate clearing of the
status bits in the PCIe capability (not the AER capability).

I think that's the right thing to do, but it's certainly not obvious
from the _OSC description in the PCI Firmware Spec r3.2.  I think we
need a pointer to the ECN that clarifies this, i.e., sec 4.5.1 of:

    System Firmware Intermediary (SFI) _OSC and DPC Updates ECN, Feb 24,
    2020, affecting PCI Firmware Specification, Rev. 3.2
    https://members.pcisig.com/wg/PCI-SIG/document/14076
   	pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &sta);
   	pcie_capability_write_word(dev, PCI_EXP_DEVSTA, sta);
   }
--
2.19.1




--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer



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