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x86/acpi: Do not attempt to bring up secondary CPUs in the kexec case

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ACPI MADT doesn't allow to offline a CPU after it was onlined. This limits
kexec: the second kernel won't be able to use more than one CPU.

To prevent a kexec kernel from onlining secondary CPUs, invalidate the mailbox
address in the ACPI MADT wakeup structure which prevents a kexec kernel to use
it.

This is safe as the booting kernel has the mailbox address cached already and
acpi_wakeup_cpu() uses the cached value to bring up the secondary CPUs.

Note: This is a Linux specific convention and not covered by the ACPI
specification.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Tao Liu <ltao@redhat.com>
Link: https://lore.kernel.org/r/20240614095904.1345461-16-kirill.shutemov@linux.intel.com
This commit is contained in:
Kirill A. Shutemov 2024-06-14 12:59:00 +03:00 committed by Borislav Petkov (AMD)
parent 6630cbce7c
commit db0936830a
1 changed files with 28 additions and 1 deletions
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29
arch/x86/kernel/acpi/madt_wakeup.c
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@ -14,6 +14,11 @@ static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox __ro_afte
static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip)
{
if (!acpi_mp_wake_mailbox_paddr) {
pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting with kexec?\n");
return -EOPNOTSUPP;
}
/*
* Remap mailbox memory only for the first call to acpi_wakeup_cpu().
*
@ -64,6 +69,28 @@ static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip)
return 0;
}
static void acpi_mp_disable_offlining(struct acpi_madt_multiproc_wakeup *mp_wake)
{
cpu_hotplug_disable_offlining();
/*
* ACPI MADT doesn't allow to offline a CPU after it was onlined. This
* limits kexec: the second kernel won't be able to use more than one CPU.
*
* To prevent a kexec kernel from onlining secondary CPUs invalidate the
* mailbox address in the ACPI MADT wakeup structure which prevents a
* kexec kernel to use it.
*
* This is safe as the booting kernel has the mailbox address cached
* already and acpi_wakeup_cpu() uses the cached value to bring up the
* secondary CPUs.
*
* Note: This is a Linux specific convention and not covered by the
* ACPI specification.
*/
mp_wake->mailbox_address = 0;
}
int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
const unsigned long end)
{
@ -77,7 +104,7 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;
cpu_hotplug_disable_offlining();
acpi_mp_disable_offlining(mp_wake);
apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);