[PATCH] x86: add a new SMP bring up way for tboot case

[Qiaowei Ren]

tboot provides a better AP wakeup mechanism based on cpu MWAIT
feature for OS/VMM. With this mechanism, system will boot faster
and will NOT require VT to be enabled. But it requires that
OS/VMM must have support it, otherwise system can never boot up.

Once this mechanism is enabled, tboot will put APs waiting in
MWAIT loops before launching kernel. kernel can check the new
flag field in v6 tboot shared page for the hint. If the bit
TB_FLAG_AP_WAKE_SUPPORT in flag field is set, kernel BSP has
to write the monitored memory (tboot->ap_wake_trigger) to bring
APs out of MWAIT loops. The sipi vector should be written in
tboot->ap_wake_addr before waking up APs.

Signed-off-by: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
Signed-off-by: Xiaoyan Zhang <xiaoyan.zhang@xxxxxxxxx>
Signed-off-by: Gang Wei <gang.wei@xxxxxxxxx>
---
 arch/x86/kernel/smpboot.c |   21 ++++++++++-----------
 arch/x86/kernel/tboot.c   |   36 ++++++++++++++++++++++++++++++++++++
 include/linux/tboot.h     |   17 +++++++++++++++++
 3 files changed, 63 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9f190a2..07f979e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -787,17 +787,16 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 		}
 	}
 
-	/*
-	 * Wake up a CPU in difference cases:
-	 * - Use the method in the APIC driver if it's defined
-	 * Otherwise,
-	 * - Use an INIT boot APIC message for APs or NMI for BSP.
-	 */
-	if (apic->wakeup_secondary_cpu)
-		boot_error = apic->wakeup_secondary_cpu(apicid, start_ip);
-	else
-		boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid,
-						     &cpu0_nmi_registered);
+	if (!tboot_wake_up(apicid, start_ip)) {
+		/*
+		 * Kick the secondary CPU. Use the method in the APIC driver
+		 * if it's defined - or use an INIT boot APIC message otherwise:
+		 */
+		if (apic->wakeup_secondary_cpu)
+			boot_error = apic->wakeup_secondary_cpu(apicid, start_ip);
+		else
+			boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip);
+	}
 
 	if (!boot_error) {
 		/*
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index f84fe00..0ec1947 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -101,6 +101,8 @@ void __init tboot_probe(void)
 	pr_debug("shutdown_entry: 0x%x\n", tboot->shutdown_entry);
 	pr_debug("tboot_base: 0x%08x\n", tboot->tboot_base);
 	pr_debug("tboot_size: 0x%x\n", tboot->tboot_size);
+	if (tboot->version >= 6)
+		pr_info("flags: 0x%08x\n", tboot->flags);
 }
 
 static pgd_t *tboot_pg_dir;
@@ -453,3 +455,37 @@ int tboot_force_iommu(void)
 
 	return 1;
 }
+
+/*
+ * tboot provides a better AP wakeup mechanism based on cpu MWAIT
+ * feature for OS/VMM. This mechanism is defaultly disabled, and
+ * could be enabled with tboot command line option:
+ *	ap_wake_mwait=true|false
+ *
+ * With this mechanism, system will boot faster and will NOT require
+ * VT to be enabled. But it requires that OS/VMM must have support
+ * it, otherwise system can never boot up.
+ *
+ * Once this mechanism is enabled, tboot will put APs waiting in
+ * MWAIT loops before launching kernel. kernel can check the new
+ * flag field in v6 tboot shared page for the hint. If the bit
+ * TB_FLAG_AP_WAKE_SUPPORT in flag field is set, kernel BSP has
+ * to write the monitored memory (tboot->ap_wake_trigger) to bring
+ * APs out of MWAIT loops. The sipi vector should be written in
+ * tboot->ap_wake_addr before waking up APs.
+ */
+bool tboot_wake_up(int apicid, unsigned long sipi_vec)
+{
+	if (!tboot_enabled())
+		return false;
+
+	if ((tboot->version < 6) ||
+		!(tboot->flags & TB_FLAG_AP_WAKE_SUPPORT))
+		return false;
+
+	tboot->ap_wake_addr = sipi_vec;
+	tboot->ap_wake_trigger = apicid;
+
+	return true;
+}
+
diff --git a/include/linux/tboot.h b/include/linux/tboot.h
index c75128b..163d779 100644
--- a/include/linux/tboot.h
+++ b/include/linux/tboot.h
@@ -124,8 +124,23 @@ struct tboot {
 
 	/* number of processors in wait-for-SIPI */
 	u32 num_in_wfs;
+
+	/*
+	 * version 6+ fields:
+	 */
+
+	u32 flags;
+
+	/* phys addr of kernel/VMM SIPI vector */
+	u64 ap_wake_addr;
+
+	/* kernel/VMM writes APIC ID to wake AP */
+	u32 ap_wake_trigger;
 } __packed;
 
+/* kernel/VMM use INIT-SIPI-SIPI if clear, ap_wake_* if set */
+#define TB_FLAG_AP_WAKE_SUPPORT 0X00000001
+
 /*
  * UUID for tboot data struct to facilitate matching
  * defined as {663C8DFF-E8B3-4b82-AABF-19EA4D057A08} by tboot, which is
@@ -146,6 +161,7 @@ extern void tboot_shutdown(u32 shutdown_type);
 extern struct acpi_table_header *tboot_get_dmar_table(
 				      struct acpi_table_header *dmar_tbl);
 extern int tboot_force_iommu(void);
+extern bool tboot_wake_up(int apicid, unsigned long sipi_vec);
 
 #else
 
@@ -156,6 +172,7 @@ extern int tboot_force_iommu(void);
 					do { } while (0)
 #define tboot_get_dmar_table(dmar_tbl)	(dmar_tbl)
 #define tboot_force_iommu()		0
+#define tboot_wake_up(apicid, sipi_vec) 0
 
 #endif /* !CONFIG_INTEL_TXT */
 
-- 
1.7.9.5

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