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 --- drivers/acpi/reboot.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 drivers/acpi/reboot.c (limited to 'drivers/acpi/reboot.c') diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c new file mode 100644 index 000000000..b79b7c99c --- /dev/null +++ b/drivers/acpi/reboot.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define pr_fmt(fmt) "ACPI: " fmt + +#include +#include +#include +#include + +#ifdef CONFIG_PCI +static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value) +{ + unsigned int devfn; + struct pci_bus *bus0; + + /* The reset register can only live on bus 0. */ + bus0 = pci_find_bus(0, 0); + if (!bus0) + return; + /* Form PCI device/function pair. */ + devfn = PCI_DEVFN((rr->address >> 32) & 0xffff, + (rr->address >> 16) & 0xffff); + pr_debug("Resetting with ACPI PCI RESET_REG.\n"); + /* Write the value that resets us. */ + pci_bus_write_config_byte(bus0, devfn, + (rr->address & 0xffff), reset_value); +} +#else +static inline void acpi_pci_reboot(struct acpi_generic_address *rr, + u8 reset_value) +{ + pr_warn_once("PCI configuration space access is not supported\n"); +} +#endif + +void acpi_reboot(void) +{ + struct acpi_generic_address *rr; + u8 reset_value; + + if (acpi_disabled) + return; + + rr = &acpi_gbl_FADT.reset_register; + + /* ACPI reset register was only introduced with v2 of the FADT */ + + if (acpi_gbl_FADT.header.revision < 2) + return; + + /* Is the reset register supported? The spec says we should be + * checking the bit width and bit offset, but Windows ignores + * these fields */ + if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER)) + return; + + reset_value = acpi_gbl_FADT.reset_value; + + /* The reset register can only exist in I/O, Memory or PCI config space + * on a device on bus 0. */ + switch (rr->space_id) { + case ACPI_ADR_SPACE_PCI_CONFIG: + acpi_pci_reboot(rr, reset_value); + break; + + case ACPI_ADR_SPACE_SYSTEM_MEMORY: + case ACPI_ADR_SPACE_SYSTEM_IO: + pr_debug("ACPI MEMORY or I/O RESET_REG.\n"); + acpi_reset(); + break; + } + + /* + * Some platforms do not shut down immediately after writing to the + * ACPI reset register, and this results in racing with the + * subsequent reboot mechanism. + * + * The 15ms delay has been found to be long enough for the system + * to reboot on the affected platforms. + */ + mdelay(15); +} -- cgit v1.3.1