As per ACPI specification r6.4, sec 5.2.12.19, a new sub
structure – multiprocessor wake-up structure - is added to the
ACPI Multiple APIC Description Table (MADT) to describe the
information of the mailbox. If a platform firmware produces the
multiprocessor wake-up structure, then OS may use this new
mailbox-based mechanism to wake up the APs.
Add ACPI MADT wake table parsing support for x86 platform and if
MADT wake table is present, update apic->wakeup_secondary_cpu with
new API which uses MADT wake mailbox to wake-up CPU.
Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Rafael J. Wysocki<rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
Changes since v6:
* Rebased on top of v5.14-rc1.
Changes since v5:
* None ( CCed ACPI list)
Changes since v4:
* Used smp_store_release() in place of WRITE_ONCE().
* Addressed some checkpatch warnings.
Changes since v3:
* Removed acpi_mp_wake_mailbox_init() and moved init code to
acpi_wakeup_cpu().
* Removed redundant NULL pointer check for acpi_mp_wake_mailbox.
* Added comments/debug prints as per Rafael's suggestion.
* Removed MADT/SVKL ACPI patches from this patchset. It will be
merged via ACPICA submission.
arch/x86/include/asm/apic.h | 3 ++
arch/x86/kernel/acpi/boot.c | 96 +++++++++++++++++++++++++++++++++++++
arch/x86/kernel/apic/apic.c | 8 ++++
3 files changed, 107 insertions(+)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 48067af94678..463905172cd0 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -488,6 +488,9 @@ static inline unsigned int read_apic_id(void)
return apic->get_apic_id(reg);
}
+typedef int (*wakeup_cpu_handler)(int apicid, unsigned long start_eip);
+extern void acpi_wake_cpu_handler_update(wakeup_cpu_handler handler);
+
extern int default_apic_id_valid(u32 apicid);
extern int default_acpi_madt_oem_check(char *, char *);
extern void default_setup_apic_routing(void);
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index e55e0c1fad8c..c2df8843950d 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -64,6 +64,10 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif
+static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
+static u64 acpi_mp_wake_mailbox_paddr;
+static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE;
+
#ifdef CONFIG_X86_IO_APIC
/*
* Locks related to IOAPIC hotplug
@@ -327,6 +331,68 @@ acpi_parse_lapic_nmi(union acpi_subtable_headers * header, const unsigned long e
return 0;
}
+static int acpi_wakeup_cpu(int apicid, unsigned long start_ip)
+{
+ u8 timeout = 0xFF;
+
+ /* Remap mailbox memory only for the first call to acpi_wakeup_cpu() */
+ if (physids_empty(apic_id_wakemap)) {
+ acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
+ sizeof(*acpi_mp_wake_mailbox),
+ MEMREMAP_WB);
+ }
+
+ /*
+ * According to the ACPI specification r6.4, sec 5.2.12.19, the
+ * mailbox-based wakeup mechanism cannot be used more than once
+ * for the same CPU, so skip sending wake commands to already
+ * awake CPU.
+ */
+ if (physid_isset(apicid, apic_id_wakemap)) {
+ pr_err("CPU already awake (APIC ID %x), skipping wakeup\n",
+ apicid);
+ return -EINVAL;
+ }
+
+ /*
+ * Mailbox memory is shared between firmware and OS. Firmware will
+ * listen on mailbox command address, and once it receives the wakeup
+ * command, CPU associated with the given apicid will be booted. So,
+ * the value of apic_id and wakeup_vector has to be set before updating
+ * the wakeup command. So use smp_store_release to let the compiler know
+ * about it and preserve the order of writes.
+ */
+ smp_store_release(&acpi_mp_wake_mailbox->apic_id, apicid);
+ smp_store_release(&acpi_mp_wake_mailbox->wakeup_vector, start_ip);
+ smp_store_release(&acpi_mp_wake_mailbox->command,
+ ACPI_MP_WAKE_COMMAND_WAKEUP);
+
+ /*
+ * After writing wakeup command, wait for maximum timeout of 0xFF
+ * for firmware to reset the command address back zero to indicate
+ * the successful reception of command.
+ * NOTE: 255 as timeout value is decided based on our experiments.
+ *
+ * XXX: Change the timeout once ACPI specification comes up with
+ * standard maximum timeout value.
+ */
+ while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--)
+ cpu_relax();
+
+ if (timeout) {
+ /*
+ * If the CPU wakeup process is successful, store the
+ * status in apic_id_wakemap to prevent re-wakeup
+ * requests.
+ */
+ physid_set(apicid, apic_id_wakemap);
+ return 0;
+ }
+
+ /* If timed out (timeout == 0), return error */
+ return -EIO;
+}
+
#endif /*CONFIG_X86_LOCAL_APIC */
#ifdef CONFIG_X86_IO_APIC
@@ -1074,6 +1140,30 @@ static int __init acpi_parse_madt_lapic_entries(void)
}
return 0;
}
+
+static int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
+ const unsigned long end)
+{
+ struct acpi_madt_multiproc_wakeup *mp_wake;
+
+ if (acpi_mp_wake_mailbox)
+ return -EINVAL;
+
+ if (!IS_ENABLED(CONFIG_SMP))
+ return -ENODEV;
+
+ mp_wake = (struct acpi_madt_multiproc_wakeup *)header;
+ if (BAD_MADT_ENTRY(mp_wake, end))
+ return -EINVAL;
+
+ acpi_table_print_madt_entry(&header->common);
+
+ acpi_mp_wake_mailbox_paddr = mp_wake->base_address;
+
+ acpi_wake_cpu_handler_update(acpi_wakeup_cpu);
+
+ return 0;
+}
#endif /* CONFIG_X86_LOCAL_APIC */
#ifdef CONFIG_X86_IO_APIC
@@ -1269,6 +1359,12 @@ static void __init acpi_process_madt(void)
smp_found_config = 1;
}
+
+ /*
+ * Parse MADT MP Wake entry.
+ */
+ acpi_table_parse_madt(ACPI_MADT_TYPE_MULTIPROC_WAKEUP,
+ acpi_parse_mp_wake, 1);
}
if (error == -EINVAL) {
/*
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index d262811ce14b..2a5b0bd16846 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2554,6 +2554,14 @@ u32 x86_msi_msg_get_destid(struct msi_msg *msg, bool extid)
}
EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid);
+void __init acpi_wake_cpu_handler_update(wakeup_cpu_handler handler)
+{
+ struct apic **drv;
+
+ for (drv = __apicdrivers; drv < __apicdrivers_end; drv++)
+ (*drv)->wakeup_secondary_cpu = handler;
+}
+
/*
* Override the generic EOI implementation with an optimized version.
* Only called during early boot when only one CPU is active and with
--
2.25.1
