Re: [PATCH 1/5] PCI/DPC: Ignore devices with no AER Capability
From: Kuppuswamy, Sathyanarayanan
Date: Sat Nov 28 2020 - 23:40:42 EST
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Olof Johansson <olof@xxxxxxxxx>
---
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