From ab84ba647f2c94ac4d0c3fc6951c49f08aa1fcf7 Mon Sep 17 00:00:00 2001 From: Zhiquan Li Date: Mon, 5 Aug 2024 18:35:31 +0800 Subject: [PATCH] x86/acpi: Remove __ro_after_init from acpi_mp_wake_mailbox On a platform using the "Multiprocessor Wakeup Structure"[1] to startup secondary CPUs the control processor needs to memremap() the physical address of the MP Wakeup Structure mailbox to the variable acpi_mp_wake_mailbox, which holds the virtual address of mailbox. To wake up the AP the control processor writes the APIC ID of AP, the wakeup vector and the ACPI_MP_WAKE_COMMAND_WAKEUP command into the mailbox. Current implementation doesn't consider the case which restricts boot time CPU bringup to 1 with the kernel parameter "maxcpus=1" and brings other CPUs online later from user space as it sets acpi_mp_wake_mailbox to read-only after init. So when the first AP is tried to brought online after init, the attempt to update the variable results in a kernel panic. The memremap() call that initializes the variable cannot be moved into acpi_parse_mp_wake() because memremap() is not functional at that point in the boot process. Also as the APs might never be brought up, keep the memremap() call in acpi_wakeup_cpu() so that the operation only takes place when needed. Fixes: 24dd05da8c79 ("x86/apic: Mark acpi_mp_wake_* variables as __ro_after_init") Signed-off-by: Zhiquan Li Signed-off-by: Thomas Gleixner Reviewed-by: Kirill A. Shutemov Link: https://lore.kernel.org/all/20240805103531.1230635-1-zhiquan1.li@intel.com --- arch/x86/kernel/acpi/madt_wakeup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c index 6cfe762be28b..d5ef6215583b 100644 --- a/arch/x86/kernel/acpi/madt_wakeup.c +++ b/arch/x86/kernel/acpi/madt_wakeup.c @@ -19,7 +19,7 @@ static u64 acpi_mp_wake_mailbox_paddr __ro_after_init; /* Virtual address of the Multiprocessor Wakeup Structure mailbox */ -static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox __ro_after_init; +static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox; static u64 acpi_mp_pgd __ro_after_init; static u64 acpi_mp_reset_vector_paddr __ro_after_init;