The bootstrap processor uses acpi_wakeup_cpu() to indicate to firmware that
it wants to boot a secondary CPU using a mailbox as described in the
Multiprocessor Wakeup Structure of the ACPI specification.
The platform firmware may implement the mailbox as described in the ACPI
specification but enumerate it using a DeviceTree graph. An example of
this is OpenHCL paravisor.
Move the code used to setup and use the mailbox for CPU wakeup out of the
ACPI directory into a new smpwakeup.c file that both ACPI and DeviceTree
can use.
No functional changes are intended.
Co-developed-by: Yunhong Jiang <yunhong.ji...@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.ji...@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
---
Changes since v3:
- Create a new file smpwakeup.c instead of relocating it to smpboot.c.
(Rafael)
Changes since v2:
- Only move to smpboot.c the portions of the code that configure and
use the mailbox. This also resolved the compile warnings about unused
functions that Michael Kelley reported.
- Edited the commit message for clarity.
Changes since v1:
- None.
---
arch/x86/Kconfig | 7 ++++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/acpi/madt_wakeup.c | 76 ----------------------------------
arch/x86/kernel/smpwakeup.c | 83 ++++++++++++++++++++++++++++++++++++++
4 files changed, 91 insertions(+), 76 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cb0f4af31789..82147edb355a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1113,6 +1113,13 @@ config X86_LOCAL_APIC
depends on X86_64 || SMP || X86_UP_APIC || PCI_MSI
select IRQ_DOMAIN_HIERARCHY
+config X86_MAILBOX_WAKEUP
+ def_bool y
+ depends on OF || ACPI_MADT_WAKEUP
+ depends on X86_64
+ depends on SMP
+ depends on X86_LOCAL_APIC
+
config ACPI_MADT_WAKEUP
def_bool y
depends on X86_64
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 99a783fd4691..8f078af42a71 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -94,6 +94,7 @@ apm-y := apm_32.o
obj-$(CONFIG_APM) += apm.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SMP) += smpboot.o
+obj-$(CONFIG_X86_MAILBOX_WAKEUP) += smpwakeup.o
obj-$(CONFIG_X86_TSC) += tsc_sync.o
obj-$(CONFIG_SMP) += setup_percpu.o
obj-$(CONFIG_X86_MPPARSE) += mpparse.o
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c
b/arch/x86/kernel/acpi/madt_wakeup.c
index 4033c804307a..a7e0158269b0 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -2,12 +2,10 @@
#include <linux/acpi.h>
#include <linux/cpu.h>
#include <linux/delay.h>
-#include <linux/io.h>
#include <linux/kexec.h>
#include <linux/memblock.h>
#include <linux/pgtable.h>
#include <linux/sched/hotplug.h>
-#include <asm/apic.h>
#include <asm/barrier.h>
#include <asm/init.h>
#include <asm/intel_pt.h>
@@ -15,12 +13,6 @@
#include <asm/processor.h>
#include <asm/reboot.h>
-/* Physical address of the Multiprocessor Wakeup Structure mailbox */
-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;
-
static u64 acpi_mp_pgd __ro_after_init;
static u64 acpi_mp_reset_vector_paddr __ro_after_init;
@@ -127,63 +119,6 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
return 0;
}
-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().
- *
- * Wakeup of secondary CPUs is fully serialized in the core code.
- * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
- */
- if (!acpi_mp_wake_mailbox) {
- acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
- sizeof(*acpi_mp_wake_mailbox),
- MEMREMAP_WB);
- }
-
- /*
- * Mailbox memory is shared between the firmware and OS. Firmware will
- * listen on mailbox command address, and once it receives the wakeup
- * command, the CPU associated with the given apicid will be booted.
- *
- * The value of 'apic_id' and 'wakeup_vector' must be visible to the
- * firmware before the wakeup command is visible. smp_store_release()
- * ensures ordering and visibility.
- */
- acpi_mp_wake_mailbox->apic_id = apicid;
- acpi_mp_wake_mailbox->wakeup_vector = start_ip;
- smp_store_release(&acpi_mp_wake_mailbox->command,
- ACPI_MP_WAKE_COMMAND_WAKEUP);
-
- /*
- * Wait for the CPU to wake up.
- *
- * The CPU being woken up is essentially in a spin loop waiting to be
- * woken up. It should not take long for it wake up and acknowledge by
- * zeroing out ->command.
- *
- * ACPI specification doesn't provide any guidance on how long kernel
- * has to wait for a wake up acknowledgment. It also doesn't provide
- * a way to cancel a wake up request if it takes too long.
- *
- * In TDX environment, the VMM has control over how long it takes to
- * wake up secondary. It can postpone scheduling secondary vCPU
- * indefinitely. Giving up on wake up request and reporting error opens
- * possible attack vector for VMM: it can wake up a secondary CPU when
- * kernel doesn't expect it. Wait until positive result of the wake up
- * request.
- */
- while (READ_ONCE(acpi_mp_wake_mailbox->command))
- cpu_relax();
-
- return 0;
-}
-
static void acpi_mp_disable_offlining(struct acpi_madt_multiproc_wakeup
*mp_wake)
{
cpu_hotplug_disable_offlining();
@@ -246,14 +181,3 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers
*header,
return 0;
}
-
-void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
-{
- acpi_mp_wake_mailbox_paddr = mailbox_paddr;
- apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
-}
-
-struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
-{
- return acpi_mp_wake_mailbox;
-}
diff --git a/arch/x86/kernel/smpwakeup.c b/arch/x86/kernel/smpwakeup.c
new file mode 100644
index 000000000000..e34ffbfffaf5
--- /dev/null
+++ b/arch/x86/kernel/smpwakeup.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/printk.h>
+#include <linux/types.h>
+#include <asm/apic.h>
+#include <asm/barrier.h>
+#include <asm/processor.h>
+
+/* Physical address of the Multiprocessor Wakeup Structure mailbox */
+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;
+
+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().
+ *
+ * Wakeup of secondary CPUs is fully serialized in the core code.
+ * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
+ */
+ if (!acpi_mp_wake_mailbox) {
+ acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
+ sizeof(*acpi_mp_wake_mailbox),
+ MEMREMAP_WB);
+ }
+
+ /*
+ * Mailbox memory is shared between the firmware and OS. Firmware will
+ * listen on mailbox command address, and once it receives the wakeup
+ * command, the CPU associated with the given apicid will be booted.
+ *
+ * The value of 'apic_id' and 'wakeup_vector' must be visible to the
+ * firmware before the wakeup command is visible. smp_store_release()
+ * ensures ordering and visibility.
+ */
+ acpi_mp_wake_mailbox->apic_id = apicid;
+ acpi_mp_wake_mailbox->wakeup_vector = start_ip;
+ smp_store_release(&acpi_mp_wake_mailbox->command,
+ ACPI_MP_WAKE_COMMAND_WAKEUP);
+
+ /*
+ * Wait for the CPU to wake up.
+ *
+ * The CPU being woken up is essentially in a spin loop waiting to be
+ * woken up. It should not take long for it wake up and acknowledge by
+ * zeroing out ->command.
+ *
+ * ACPI specification doesn't provide any guidance on how long kernel
+ * has to wait for a wake up acknowledgment. It also doesn't provide
+ * a way to cancel a wake up request if it takes too long.
+ *
+ * In TDX environment, the VMM has control over how long it takes to
+ * wake up secondary. It can postpone scheduling secondary vCPU
+ * indefinitely. Giving up on wake up request and reporting error opens
+ * possible attack vector for VMM: it can wake up a secondary CPU when
+ * kernel doesn't expect it. Wait until positive result of the wake up
+ * request.
+ */
+ while (READ_ONCE(acpi_mp_wake_mailbox->command))
+ cpu_relax();
+
+ return 0;
+}
+
+void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
+{
+ acpi_mp_wake_mailbox_paddr = mailbox_paddr;
+ apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
+}
+
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+ return acpi_mp_wake_mailbox;
+}
--
2.43.0
