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, 136 insertions, 0 deletions

diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
new file mode 100644
index 000000000..5866195de
--- /dev/null
+++ b/drivers/tty/hvc/Kconfig
@@ -0,0 +1,136 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config HVC_DRIVER
+	bool
+	help
+	  Generic "hypervisor virtual console" infrastructure for various
+	  hypervisors (pSeries, iSeries, Xen).
+	  It will automatically be selected if one of the back-end console drivers
+	  is selected.
+
+config HVC_IRQ
+	bool
+
+config HVC_CONSOLE
+	bool "pSeries Hypervisor Virtual Console support"
+	depends on PPC_PSERIES
+	select HVC_DRIVER
+	select HVC_IRQ
+	help
+	  pSeries machines when partitioned support a hypervisor virtual
+	  console. This driver allows each pSeries partition to have a console
+	  which is accessed via the HMC.
+
+config HVC_OLD_HVSI
+	bool "Old driver for pSeries serial port (/dev/hvsi*)"
+	depends on HVC_CONSOLE
+
+config HVC_OPAL
+	bool "OPAL Console support"
+	depends on PPC_POWERNV
+	select HVC_DRIVER
+	select HVC_IRQ
+	default y
+	help
+	  PowerNV machines running under OPAL need that driver to get a console
+
+config HVC_RTAS
+	bool "IBM RTAS Console support"
+	depends on PPC_RTAS
+	select HVC_DRIVER
+	help
+	  IBM Console device driver which makes use of RTAS
+
+config HVC_IUCV
+	bool "z/VM IUCV Hypervisor console support (VM only)"
+	depends on S390 && NET
+	select HVC_DRIVER
+	select IUCV
+	default y
+	help
+	  This driver provides a Hypervisor console (HVC) back-end to access
+	  a Linux (console) terminal via a z/VM IUCV communication path.
+
+config HVC_XEN
+	bool "Xen Hypervisor Console support"
+	depends on XEN
+	select HVC_DRIVER
+	select HVC_IRQ
+	default y
+	help
+	  Xen virtual console device driver
+
+config HVC_XEN_FRONTEND
+	bool "Xen Hypervisor Multiple Consoles support"
+	depends on HVC_XEN
+	select XEN_XENBUS_FRONTEND
+	default y
+	help
+	  Xen driver for secondary virtual consoles
+
+config HVC_UDBG
+	bool "udbg based fake hypervisor console"
+	depends on PPC
+	select HVC_DRIVER
+	help
+	  This is meant to be used during HW bring up or debugging when
+	  no other console mechanism exist but udbg, to get you a quick
+	  console for userspace. Do NOT enable in production kernels.
+
+config HVC_DCC
+	bool "ARM JTAG DCC console"
+	depends on (ARM && (CPU_V6 || CPU_V6K || CPU_V7)) || ARM64
+	select HVC_DRIVER
+	select SERIAL_CORE_CONSOLE
+	help
+	  This console uses the JTAG DCC on ARM to create a console under the HVC
+	  driver. This console is used through a JTAG only on ARM. If you don't have
+	  a JTAG then you probably don't want this option.
+
+config HVC_DCC_SERIALIZE_SMP
+	bool "Use DCC only on CPU core 0"
+	depends on SMP && HVC_DCC
+	help
+	  This is a DEBUG option to serialize all console input and output to CPU 0.
+	  Some external debuggers, do not handle reads/writes from/to DCC on more
+	  than one CPU core. Each core has its own DCC device registers, so when a
+	  CPU core reads or writes from/to DCC, it only accesses its own DCC device.
+	  Since kernel code can run on any CPU core, every time the kernel wants to
+	  write to the console, it might write to a different DCC.
+
+	  In SMP mode, external debuggers create multiple windows, and each window
+	  shows the DCC output only from that core's DCC. The result is that
+	  console output is either lost or scattered across windows.
+
+	  Enable this option only if you are sure that you do not need features like
+	  CPU hotplug to work. For example, during early chipset bringups without
+	  debug serial console support. If unsure, say N.
+
+config HVC_RISCV_SBI
+	bool "RISC-V SBI console support"
+	depends on RISCV_SBI && NONPORTABLE
+	select HVC_DRIVER
+	help
+	  This enables support for console output via RISC-V SBI calls, which
+	  is normally used only during boot to output printk.  This driver
+	  conflicts with real console drivers and should not be enabled on
+	  systems that directly access the console.
+
+	  If you don't know what do to here, say N.
+
+config HVCS
+	tristate "IBM Hypervisor Virtual Console Server support"
+	depends on PPC_PSERIES && HVC_CONSOLE
+	help
+	  Partitionable IBM Power5 ppc64 machines allow hosting of
+	  firmware virtual consoles from one Linux partition by
+	  another Linux partition.  This driver allows console data
+	  from Linux partitions to be accessed through TTY device
+	  interfaces in the device tree of a Linux partition running
+	  this driver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called hvcs.  Additionally, this module
+	  will depend on arch specific APIs exported from hvcserver.ko
+	  which will also be compiled when this driver is built as a
+	  module.