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, 101 insertions, 0 deletions

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
new file mode 100644
index 000000000..b9d6e1c22
--- /dev/null
+++ b/drivers/vfio/Kconfig
@@ -0,0 +1,101 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig VFIO
+	tristate "VFIO Non-Privileged userspace driver framework"
+	select IOMMU_API
+	depends on IOMMUFD || !IOMMUFD
+	select INTERVAL_TREE
+	select VFIO_GROUP if SPAPR_TCE_IOMMU || IOMMUFD=n
+	select VFIO_DEVICE_CDEV if !VFIO_GROUP
+	select VFIO_CONTAINER if IOMMUFD=n
+	help
+	  VFIO provides a framework for secure userspace device drivers.
+	  See Documentation/driver-api/vfio.rst for more details.
+
+	  If you don't know what to do here, say N.
+
+if VFIO
+config VFIO_DEVICE_CDEV
+	bool "Support for the VFIO cdev /dev/vfio/devices/vfioX"
+	depends on IOMMUFD && !SPAPR_TCE_IOMMU
+	default !VFIO_GROUP
+	help
+	  The VFIO device cdev is another way for userspace to get device
+	  access. Userspace gets device fd by opening device cdev under
+	  /dev/vfio/devices/vfioX, and then bind the device fd with an iommufd
+	  to set up secure DMA context for device access.
+
+	  If you don't know what to do here, say N.
+
+config VFIO_GROUP
+	bool "Support for the VFIO group /dev/vfio/$group_id"
+	default y
+	help
+	   VFIO group support provides the traditional model for accessing
+	   devices through VFIO and is used by the majority of userspace
+	   applications and drivers making use of VFIO.
+
+	   If you don't know what to do here, say Y.
+
+config VFIO_CONTAINER
+	bool "Support for the VFIO container /dev/vfio/vfio"
+	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
+	depends on VFIO_GROUP
+	default y
+	help
+	  The VFIO container is the classic interface to VFIO for establishing
+	  IOMMU mappings. If N is selected here then IOMMUFD must be used to
+	  manage the mappings.
+
+	  Unless testing IOMMUFD say Y here.
+
+if VFIO_CONTAINER
+config VFIO_IOMMU_TYPE1
+	tristate
+	default n
+
+config VFIO_IOMMU_SPAPR_TCE
+	tristate
+	depends on SPAPR_TCE_IOMMU
+	default VFIO
+endif
+
+config VFIO_NOIOMMU
+	bool "VFIO No-IOMMU support"
+	depends on VFIO_GROUP || (VFIO_DEVICE_CDEV && !GENERIC_ATOMIC64)
+	depends on !VFIO_GROUP || VFIO_CONTAINER || IOMMUFD_VFIO_CONTAINER
+	select IOMMUFD_NOIOMMU if VFIO_DEVICE_CDEV && !GENERIC_ATOMIC64
+	help
+	  VFIO is built on the ability to isolate devices using the IOMMU.
+	  Only with an IOMMU can userspace access to DMA capable devices be
+	  considered secure.  VFIO No-IOMMU mode enables IOMMU groups for
+	  devices without IOMMU backing for the purpose of re-using the VFIO
+	  infrastructure in a non-secure mode.  Use of this mode will result
+	  in an unsupportable kernel and will therefore taint the kernel.
+	  Device assignment to virtual machines is also not possible with
+	  this mode since there is no IOMMU to provide DMA translation.
+
+	  If you don't know what to do here, say N.
+
+config VFIO_VIRQFD
+	bool
+	select EVENTFD
+	default n
+
+config VFIO_DEBUGFS
+	bool "Export VFIO internals in DebugFS"
+	depends on DEBUG_FS
+	help
+	  Allows exposure of VFIO device internals. This option enables
+	  the use of debugfs by VFIO drivers as required. The device can
+	  cause the VFIO code create a top-level debug/vfio directory
+	  during initialization, and then populate a subdirectory with
+	  entries as required.
+
+source "drivers/vfio/pci/Kconfig"
+source "drivers/vfio/platform/Kconfig"
+source "drivers/vfio/mdev/Kconfig"
+source "drivers/vfio/fsl-mc/Kconfig"
+source "drivers/vfio/cdx/Kconfig"
+endif
+
+source "virt/lib/Kconfig"