x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 57 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-vfio b/Documentation/ABI/testing/debugfs-vfio
new file mode 100644
index 000000000..ed2f29c3a
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-vfio
@@ -0,0 +1,57 @@
+What:		/sys/kernel/debug/vfio
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	This debugfs file directory is used for debugging
+		of vfio devices, it's a common directory for all vfio devices.
+		Vfio core will create a device subdirectory under this
+		directory.
+
+What:		/sys/kernel/debug/vfio/<device>/migration
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	This debugfs file directory is used for debugging
+		of vfio devices that support live migration.
+		The debugfs of each vfio device that supports live migration
+		could be created under this directory.
+
+What:		/sys/kernel/debug/vfio/<device>/migration/state
+Date:		December 2023
+KernelVersion:	6.8
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	Read the live migration status of the vfio device.
+		The contents of the state file reflects the migration state
+		relative to those defined in the vfio_device_mig_state enum
+
+What:		/sys/kernel/debug/vfio/<device>/migration/features
+Date:		Oct 2025
+KernelVersion:	6.18
+Contact:	Cédric Le Goater <clg@redhat.com>
+Description:	Read the migration features of the vfio device.
+
+What:		/sys/kernel/debug/vfio/<device>/pci
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	This debugfs file directory is used for debugging
+		VFIO PCI devices.
+
+What:		/sys/kernel/debug/vfio/<device>/pci/nointxmask
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	Read the nointxmask policy latched for this device.  This
+		policy governs whether the device may use PCI 2.3 style
+		INTx masking when supported, reporting a value of "N", or
+		requires APIC level INTx masking, reporting a value of "Y".
+
+What:		/sys/kernel/debug/vfio/<device>/pci/disable_idle_d3
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alex Williamson <alex.williamson@nvidia.com>
+Description:	Read the disable_idle_d3 policy latched for this device.  This
+		policy governs whether the device PM runtime usage count is
+		kept elevated while the device is bound to the driver and
+		unused, reporting a value of "Y", or decremented to allow the
+		device to enter a low power state, reporting a value of "N".