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, 89 insertions, 0 deletions

diff --git a/arch/alpha/lib/strrchr.S b/arch/alpha/lib/strrchr.S
new file mode 100644
index 000000000..dd8e073b6
--- /dev/null
+++ b/arch/alpha/lib/strrchr.S
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * arch/alpha/lib/strrchr.S
+ * Contributed by Richard Henderson (rth@tamu.edu)
+ *
+ * Return the address of the last occurrence of a given character
+ * within a null-terminated string, or null if it is not found.
+ */
+#include <linux/export.h>
+#include <asm/regdef.h>
+
+	.set noreorder
+	.set noat
+
+	.align 3
+	.ent strrchr
+	.globl strrchr
+strrchr:
+	.frame sp, 0, ra
+	.prologue 0
+
+	zapnot	a1, 1, a1	# e0    : zero extend our test character
+	mov	zero, t6	# .. e1 : t6 is last match aligned addr
+	sll	a1, 8, t5	# e0    : replicate our test character
+	mov	zero, t8	# .. e1 : t8 is last match byte compare mask
+	or	t5, a1, a1	# e0    :
+	ldq_u   t0, 0(a0)	# .. e1 : load first quadword
+	sll	a1, 16, t5	# e0    :
+	andnot  a0, 7, v0	# .. e1 : align source addr
+	or	t5, a1, a1	# e0    :
+	lda	t4, -1		# .. e1 : build garbage mask
+	sll	a1, 32, t5	# e0    :
+	cmpbge  zero, t0, t1	# .. e1 : bits set iff byte == zero
+	mskqh	t4, a0, t4	# e0    :
+	or	t5, a1, a1	# .. e1 : character replication complete
+	xor	t0, a1, t2	# e0    : make bytes == c zero
+	cmpbge	zero, t4, t4	# .. e1 : bits set iff byte is garbage
+	cmpbge  zero, t2, t3	# e0    : bits set iff byte == c
+	andnot	t1, t4, t1	# .. e1 : clear garbage from null test
+	andnot	t3, t4, t3	# e0    : clear garbage from char test
+	bne	t1, $eos	# .. e1 : did we already hit the terminator?
+
+	/* Character search main loop */
+$loop:
+	ldq	t0, 8(v0)	# e0    : load next quadword
+	cmovne	t3, v0, t6	# .. e1 : save previous comparisons match
+	cmovne	t3, t3, t8	# e0    :
+	addq	v0, 8, v0	# .. e1 :
+	xor	t0, a1, t2	# e0    :
+	cmpbge	zero, t0, t1	# .. e1 : bits set iff byte == zero
+	cmpbge	zero, t2, t3	# e0    : bits set iff byte == c
+	beq	t1, $loop	# .. e1 : if we havnt seen a null, loop
+
+	/* Mask out character matches after terminator */
+$eos:
+	negq	t1, t4		# e0    : isolate first null byte match
+	and	t1, t4, t4	# e1    :
+	subq	t4, 1, t5	# e0    : build a mask of the bytes up to...
+	or	t4, t5, t4	# e1    : ... and including the null
+
+	and	t3, t4, t3	# e0    : mask out char matches after null
+	cmovne	t3, t3, t8	# .. e1 : save it, if match found
+	cmovne	t3, v0, t6	# e0    :
+
+	/* Locate the address of the last matched character */
+
+	/* Retain the early exit for the ev4 -- the ev5 mispredict penalty
+	   is 5 cycles -- the same as just falling through.  */
+	beq	t8, $retnull	# .. e1 :
+
+	and	t8, 0xf0, t2	# e0    : binary search for the high bit set
+	cmovne	t2, t2, t8	# .. e1 (zdb)
+	cmovne	t2, 4, t2	# e0    :
+	and	t8, 0xcc, t1	# .. e1 :
+	cmovne	t1, t1, t8	# e0    :
+	cmovne	t1, 2, t1	# .. e1 :
+	and	t8, 0xaa, t0	# e0    :
+	cmovne	t0, 1, t0	# .. e1 (zdb)
+	addq	t2, t1, t1	# e0    :
+	addq	t6, t0, v0	# .. e1 : add our aligned base ptr to the mix
+	addq	v0, t1, v0	# e0    :
+	ret			# .. e1 :
+
+$retnull:
+	mov	zero, v0	# e0    :
+	ret			# .. e1 :
+
+	.end strrchr
+	EXPORT_SYMBOL(strrchr)