From 27600805e62f800bacf990354632eae4e487d34c Mon Sep 17 00:00:00 2001 From: Yazen Ghannam Date: Thu, 3 Sep 2026 10:43:25 -0500 Subject: x86/amd_node: Fix PCI device reference counting in amd_smn_init() 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 Assisted-by: LLM Signed-off-by: Yazen Ghannam Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Mario Limonciello (AMD) Cc: Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com --- arch/arm/common/vlock.S | 101 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 arch/arm/common/vlock.S (limited to 'arch/arm/common/vlock.S') diff --git a/arch/arm/common/vlock.S b/arch/arm/common/vlock.S new file mode 100644 index 000000000..c5eaed5a7 --- /dev/null +++ b/arch/arm/common/vlock.S @@ -0,0 +1,101 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * vlock.S - simple voting lock implementation for ARM + * + * Created by: Dave Martin, 2012-08-16 + * Copyright: (C) 2012-2013 Linaro Limited + * + * This algorithm is described in more detail in + * Documentation/arch/arm/vlocks.rst. + */ + +#include +#include "vlock.h" + +.arch armv7-a + +/* Select different code if voting flags can fit in a single word. */ +#if VLOCK_VOTING_SIZE > 4 +#define FEW(x...) +#define MANY(x...) x +#else +#define FEW(x...) x +#define MANY(x...) +#endif + +@ voting lock for first-man coordination + +.macro voting_begin rbase:req, rcpu:req, rscratch:req + mov \rscratch, #1 + strb \rscratch, [\rbase, \rcpu] + dmb +.endm + +.macro voting_end rbase:req, rcpu:req, rscratch:req + dmb + mov \rscratch, #0 + strb \rscratch, [\rbase, \rcpu] + dsb st + sev +.endm + +/* + * The vlock structure must reside in Strongly-Ordered or Device memory. + * This implementation deliberately eliminates most of the barriers which + * would be required for other memory types, and assumes that independent + * writes to neighbouring locations within a cacheline do not interfere + * with one another. + */ + +@ r0: lock structure base +@ r1: CPU ID (0-based index within cluster) +ENTRY(vlock_trylock) + add r1, r1, #VLOCK_VOTING_OFFSET + + voting_begin r0, r1, r2 + + ldrb r2, [r0, #VLOCK_OWNER_OFFSET] @ check whether lock is held + cmp r2, #VLOCK_OWNER_NONE + bne trylock_fail @ fail if so + + @ Control dependency implies strb not observable before previous ldrb. + + strb r1, [r0, #VLOCK_OWNER_OFFSET] @ submit my vote + + voting_end r0, r1, r2 @ implies DMB + + @ Wait for the current round of voting to finish: + + MANY( mov r3, #VLOCK_VOTING_OFFSET ) +0: + MANY( ldr r2, [r0, r3] ) + FEW( ldr r2, [r0, #VLOCK_VOTING_OFFSET] ) + cmp r2, #0 + wfene + bne 0b + MANY( add r3, r3, #4 ) + MANY( cmp r3, #VLOCK_VOTING_OFFSET + VLOCK_VOTING_SIZE ) + MANY( bne 0b ) + + @ Check who won: + + dmb + ldrb r2, [r0, #VLOCK_OWNER_OFFSET] + eor r0, r1, r2 @ zero if I won, else nonzero + bx lr + +trylock_fail: + voting_end r0, r1, r2 + mov r0, #1 @ nonzero indicates that I lost + bx lr +ENDPROC(vlock_trylock) + +@ r0: lock structure base +ENTRY(vlock_unlock) + dmb + mov r1, #VLOCK_OWNER_NONE + strb r1, [r0, #VLOCK_OWNER_OFFSET] + dsb st + sev + bx lr +ENDPROC(vlock_unlock) -- cgit v1.3.1