[Devel] [PATCH vz10 v2 1/3] core: add skip_pci_blacklist option to probe RHEL-disabled devices

[Konstantin Khorenko <khorenko@virtuozzo.com>]

From: Alexey Kuznetsov <kuznet@virtuozzo.com>

RHEL refuses to drive the PCI IDs listed in rh_disabled_pci_devices[]:
pci_rh_check_status() matches the device and local_pci_probe() turns
the match into -EACCES, so no driver ever binds to it. The list is a
hardware lifecycle decision rather than a statement about a defect,
and a host whose only NIC or HBA is on it cannot be deployed at all.

Keep probing such a device when skip_pci_blacklist is set. It is still
reported, as unmaintained rather than disabled, so a support dump shows
that the hardware gets no testing and no fixes.

The option is writable at runtime and the list is consulted on every
probe, so a blacklisted device can be brought up without a reboot: set
the option and rebind the device through
/sys/bus/pci/drivers/<driver>/bind.

https://virtuozzo.atlassian.net/browse/VSTOR-145697
Feature: pci: bypass the RHEL disabled device blacklist

Signed-off-by: Alexey Kuznetsov <kuznet@virtuozzo.com>
Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 12 ++++++++++++
 kernel/rh_messages.c                            |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 96ffb86cfa762..aea11ef7d28dc 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6313,6 +6313,18 @@
 			apic=verbose is specified.
 			Example: apic=debug show_lapic=all
 
+	skip_pci_blacklist
+			[KNL] Bind drivers to the PCI devices that RHEL lists
+			as disabled, instead of failing their probe. Such a
+			device is reported as unmaintained hardware: it gets
+			no testing and no fixes.
+			Also writable at runtime through
+			/sys/module/kernel/parameters/skip_pci_blacklist, and
+			the list is consulted on every probe, so a device can
+			be brought up by rebinding it afterwards.
+			Format: { "0" | "1" }
+			Default: 0
+
 	slab_debug[=options[,slabs][;[options[,slabs]]...]	[MM]
 			Enabling slab_debug allows one to determine the
 			culprit if slab objects become corrupted. Enabling
diff --git a/kernel/rh_messages.c b/kernel/rh_messages.c
index bb69e8965748b..ac3c8bebb8512 100644
--- a/kernel/rh_messages.c
+++ b/kernel/rh_messages.c
@@ -149,6 +149,9 @@ static void pci_hw_unmaintained(struct pci_dev *dev)
 				   dev->device, dev->vendor, pci_name(dev));
 }
 
+static bool skip_pci_blacklist;
+core_param(skip_pci_blacklist, skip_pci_blacklist, bool, 0644);
+
 /**
  * pci_hw_disabled() - Mark a PCI device disabled.
  * @dev: the PCI device structure to match against
@@ -164,6 +167,12 @@ static bool __maybe_unused pci_hw_disabled(struct pci_dev *dev)
 	if (!ret)
 		return false;
 
+	if (skip_pci_blacklist) {
+		mark_hardware_unmaintained(dev_driver_string(&dev->dev), "%04X:%04X @ %s",
+					   dev->device, dev->vendor, pci_name(dev));
+		return false;
+	}
+
 	mark_hardware_disabled(dev_driver_string(&dev->dev), "%04X:%04X @ %s",
 				   dev->device, dev->vendor, pci_name(dev));
 	return true;

-- 
2.43.0

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