PCI: Revert the cfg_access_lock lockdep mechanism

JIRA: https://issues.redhat.com/browse/RHEL-50255
Upstream Status: c9d52fb

commit c9d52fb
Author: Dan Williams <dan.j.williams@intel.com>
Date:   Thu May 30 18:04:24 2024 -0700

    PCI: Revert the cfg_access_lock lockdep mechanism

    While the experiment did reveal that there are additional places that are
    missing the lock during secondary bus reset, one of the places that needs
    to take cfg_access_lock (pci_bus_lock()) is not prepared for lockdep
    annotation.

    Specifically, pci_bus_lock() takes pci_dev_lock() recursively and is
    currently dependent on the fact that the device_lock() is marked
    lockdep_set_novalidate_class(&dev->mutex). Otherwise, without that
    annotation, pci_bus_lock() would need to use something like a new
    pci_dev_lock_nested() helper, a scheme to track a PCI device's depth in the
    topology, and a hope that the depth of a PCI tree never exceeds the max
    value for a lockdep subclass.

    The alternative to ripping out the lockdep coverage would be to deploy a
    dynamic lock key for every PCI device. Unfortunately, there is evidence
    that increasing the number of keys that lockdep needs to track to be
    per-PCI-device is prohibitively expensive for something like the
    cfg_access_lock.

    The main motivation for adding the annotation in the first place was to
    catch unlocked secondary bus resets, not necessarily catch lock ordering
    problems between cfg_access_lock and other locks. Solve that narrower
    problem with follow-on patches, and just due to targeted revert for now.

    Link: https://lore.kernel.org/r/171711746402.1628941.14575335981264103013.stgit@dwillia2-xfh.jf.intel.com
    Fixes: 7e89efc ("PCI: Lock upstream bridge for pci_reset_function()")
    Reported-by: Imre Deak <imre.deak@intel.com>
    Closes: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_134186v1/shard-dg2-1/igt@device_reset@unbind-reset-rebind.html
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    Tested-by: Hans de Goede <hdegoede@redhat.com>
    Tested-by: Kalle Valo <kvalo@kernel.org>
    Reviewed-by: Dave Jiang <dave.jiang@intel.com>
    Cc: Jani Saarinen <jani.saarinen@intel.com>

Signed-off-by: Myron Stowe <mstowe@redhat.com>

Author: Myron Stowe

drivers/pci/access.c

@@ -289,8 +289,6 @@ void pci_cfg_access_lock(struct pci_dev *dev)
 {
 	might_sleep();
 
-	lock_map_acquire(&dev->cfg_access_lock);
-
 	raw_spin_lock_irq(&pci_lock);
 	if (dev->block_cfg_access)
 		pci_wait_cfg(dev);
@@ -345,8 +343,6 @@ void pci_cfg_access_unlock(struct pci_dev *dev)
 	raw_spin_unlock_irqrestore(&pci_lock, flags);
 
 	wake_up_all(&pci_cfg_wait);
-
-	lock_map_release(&dev->cfg_access_lock);
 }
 EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);
 

drivers/pci/pci.c

@@ -4883,7 +4883,6 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
  */
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
 {
-	lock_map_assert_held(&dev->cfg_access_lock);
 	pcibios_reset_secondary_bus(dev);
 
 	return pci_bridge_wait_for_secondary_bus(dev, "bus reset");

drivers/pci/probe.c

@@ -2546,9 +2546,6 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 	dev->dev.dma_mask = &dev->dma_mask;
 	dev->dev.dma_parms = &dev->dma_parms;
 	dev->dev.coherent_dma_mask = 0xffffffffull;
-	lockdep_register_key(&dev->cfg_access_key);
-	lockdep_init_map(&dev->cfg_access_lock, dev_name(&dev->dev),
-			 &dev->cfg_access_key, 0);
 
 	dma_set_max_seg_size(&dev->dev, 65536);
 	dma_set_seg_boundary(&dev->dev, 0xffffffff);

include/linux/lockdep.h

@@ -354,9 +354,6 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 		.wait_type_inner = _wait_type,		\
 		.lock_type = LD_LOCK_WAIT_OVERRIDE, }
 
-#define lock_map_assert_held(l)		\
-	lockdep_assert(lock_is_held(l) != LOCK_STATE_NOT_HELD)
-
 #else /* !CONFIG_LOCKDEP */
 
 static inline void lockdep_init_task(struct task_struct *task)
@@ -448,8 +445,6 @@ extern int lockdep_is_held(const void *);
 #define DEFINE_WAIT_OVERRIDE_MAP(_name, _wait_type)	\
 	struct lockdep_map __maybe_unused _name = {}
 
-#define lock_map_assert_held(l)			do { (void)(l); } while (0)
-
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_PROVE_LOCKING

include/linux/pci.h

@@ -418,8 +418,6 @@ struct pci_dev {
 	struct resource driver_exclusive_resource;	 /* driver exclusive resource ranges */
 
 	bool		match_driver;		/* Skip attaching driver */
-	struct lock_class_key cfg_access_key;
-	struct lockdep_map cfg_access_lock;
 
 	unsigned int	transparent:1;		/* Subtractive decode bridge */
 	unsigned int	io_window:1;		/* Bridge has I/O window */