Messages in this thread |  | | Subject | Re: [PATCH 1/5] PCI/DPC: Ignore devices with no AER Capability | From | "Kuppuswamy, Sathyanarayanan" <> | Date | Sat, 28 Nov 2020 20:32:32 -0800 |
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On 11/28/20 3:25 PM, Bjorn Helgaas wrote: > On Sat, Nov 28, 2020 at 01:56:23PM -0800, Kuppuswamy, Sathyanarayanan wrote: >> On 11/28/20 1:53 PM, Bjorn Helgaas wrote: >>> On Sat, Nov 28, 2020 at 01:49:46PM -0800, Kuppuswamy, Sathyanarayanan wrote: >>>> On 11/28/20 12:24 PM, Bjorn Helgaas wrote: >>>>> On Wed, Nov 25, 2020 at 06:01:57PM -0800, Kuppuswamy, Sathyanarayanan wrote: >>>>>> On 11/25/20 5:18 PM, Bjorn Helgaas wrote: >>>>>>> From: Bjorn Helgaas <bhelgaas@google.com> >>>>>>> >>>>>>> Downstream Ports may support DPC regardless of whether they support AER >>>>>>> (see PCIe r5.0, sec 6.2.10.2). Previously, if the user booted with >>>>>>> "pcie_ports=dpc-native", it was possible for dpc_probe() to succeed even if >>>>>>> the device had no AER Capability, but dpc_get_aer_uncorrect_severity() >>>>>>> depends on the AER Capability. >>>>>>> >>>>>>> dpc_probe() previously failed if: >>>>>>> >>>>>>> !pcie_aer_is_native(pdev) && !pcie_ports_dpc_native >>>>>>> !(pcie_aer_is_native() || pcie_ports_dpc_native) # by De Morgan's law >>>>>>> >>>>>>> so it succeeded if: >>>>>>> >>>>>>> pcie_aer_is_native() || pcie_ports_dpc_native >>>>>>> >>>>>>> Fail dpc_probe() if the device has no AER Capability. >>>>>>> >>>>>>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> >>>>>>> Cc: Olof Johansson <olof@lixom.net> >>>>>>> --- >>>>>>> drivers/pci/pcie/dpc.c | 3 +++ >>>>>>> 1 file changed, 3 insertions(+) >>>>>>> >>>>>>> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c >>>>>>> index e05aba86a317..ed0dbc43d018 100644 >>>>>>> --- a/drivers/pci/pcie/dpc.c >>>>>>> +++ b/drivers/pci/pcie/dpc.c >>>>>>> @@ -287,6 +287,9 @@ static int dpc_probe(struct pcie_device *dev) >>>>>>> int status; >>>>>>> u16 ctl, cap; >>>>>>> + if (!pdev->aer_cap) >>>>>>> + return -ENOTSUPP; >>>>>> Don't we check aer_cap support in drivers/pci/pcie/portdrv_core.c ? >>>>>> >>>>>> We don't enable DPC service, if AER service is not enabled. And AER >>>>>> service is only enabled if AER capability is supported. >>>>>> >>>>>> So dpc_probe() should not happen if AER capability is not supported? >>>>> >>>>> I don't think that's always true. If I'm reading this right, we have >>>>> this: >>>>> >>>>> get_port_device_capability(...) >>>>> { >>>>> #ifdef CONFIG_PCIEAER >>>>> if (dev->aer_cap && ...) >>>>> services |= PCIE_PORT_SERVICE_AER; >>>>> #endif >>>>> >>>>> if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC) && >>>>> pci_aer_available() && >>>>> (pcie_ports_dpc_native || (services & PCIE_PORT_SERVICE_AER))) >>>>> services |= PCIE_PORT_SERVICE_DPC; >>>>> } >>>>> >>>>> and in the case where: >>>>> >>>>> - CONFIG_PCIEAER=y >>>>> - booted with "pcie_ports=dpc-native" (pcie_ports_dpc_native is true) >>>>> - "dev" has no AER capability >>>>> - "dev" has DPC capability >>>>> >>>>> I think we do enable PCIE_PORT_SERVICE_DPC. >>>> Got it. But further looking into it, I am wondering whether >>>> we should keep this dependency? Currently we just use it to >>>> dump the error information. Do we need to create dependency >>>> between DPC and AER (which is functionality not dependent) just >>>> to see more details about the error? >>> >>> That's a good question, but I don't really want to get into the actual >>> operation of the AER and DPC drivers in this series, so maybe >>> something we should explore later. > >> In that case, can you move this check to >> drivers/pci/pcie/portdrv_core.c? I don't see the point of >> distributed checks in both get_port_device_capability() and >> dpc_probe(). > > I totally agree that these distributed checks are terrible, but my > long-term hope is to get rid of portdrv and handle these "services" > more like we handle other capabilities. For example, maybe we can > squash dpc_probe() into pci_dpc_init(), so I'd actually like to move > things from get_port_device_capability() into dpc_probe(). Removing the service driver model will be a major overhaul. It would affect even the error recovery drivers. You can find motivation for service drivers in Documentation/PCI/pciebus-howto.rst.
But till we fix this part, I recommend grouping all dependency checks to one place (either dpc_probe() or portdrv service driver). >
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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