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cpu/hotplug, x86/acpi: Disable CPU offlining for ACPI MADT wakeup

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ACPI MADT doesn't allow to offline a CPU after it has been woken up.

Currently, CPU hotplug is prevented based on the confidential computing
attribute which is set for Intel TDX. But TDX is not the only possible user of
the wake up method. Any platform that uses ACPI MADT wakeup method cannot
offline CPU.

Disable CPU offlining on ACPI MADT wakeup enumeration.

This has no visible effects for users: currently, TDX guest is the only platform
that uses the ACPI MADT wakeup method.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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/20240614095904.1345461-5-kirill.shutemov@linux.intel.com
This commit is contained in:
Kirill A. Shutemov 2024-06-14 12:58:49 +03:00 committed by Borislav Petkov (AMD)
parent 1037e4c53e
commit 66e48e491d
4 changed files with 4 additions and 13 deletions
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1
arch/x86/coco/core.c
View File

@ -29,7 +29,6 @@ static bool noinstr intel_cc_platform_has(enum cc_attr attr)
{
switch (attr) {
case CC_ATTR_GUEST_UNROLL_STRING_IO:
case CC_ATTR_HOTPLUG_DISABLED:
case CC_ATTR_GUEST_MEM_ENCRYPT:
case CC_ATTR_MEM_ENCRYPT:
return true;

3
arch/x86/kernel/acpi/madt_wakeup.c
View File

@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/acpi.h>
#include <linux/cpu.h>
#include <linux/io.h>
#include <asm/apic.h>
#include <asm/barrier.h>
@ -76,6 +77,8 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
acpi_mp_wake_mailbox_paddr = mp_wake->base_address;
cpu_hotplug_disable_offlining();
apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
return 0;

10
include/linux/cc_platform.h
View File

@ -81,16 +81,6 @@ enum cc_attr {
*/
CC_ATTR_GUEST_SEV_SNP,
/**
* @CC_ATTR_HOTPLUG_DISABLED: Hotplug is not supported or disabled.
*
* The platform/OS is running as a guest/virtual machine does not
* support CPU hotplug feature.
*
* Examples include TDX Guest.
*/
CC_ATTR_HOTPLUG_DISABLED,
/**
* @CC_ATTR_HOST_SEV_SNP: AMD SNP enabled on the host.
*

3
kernel/cpu.c
View File

@ -1481,8 +1481,7 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
* If the platform does not support hotplug, report it explicitly to
* differentiate it from a transient offlining failure.
*/
if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED) ||
cpu_hotplug_offline_disabled)
if (cpu_hotplug_offline_disabled)
return -EOPNOTSUPP;
if (cpu_hotplug_disabled)
return -EBUSY;