5 files changed, 36 insertions, 9 deletions

diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
index e13b0b49fcdf..d7249f4c90f1 100644
--- a/arch/x86/xen/pmu.c
+++ b/arch/x86/xen/pmu.c
@@ -512,10 +512,7 @@ irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id)
 	return ret;
 }
 
-bool is_xen_pmu(int cpu)
-{
-	return (get_xenpmu_data() != NULL);
-}
+bool is_xen_pmu;
 
 void xen_pmu_init(int cpu)
 {
@@ -526,7 +523,7 @@ void xen_pmu_init(int cpu)
 
 	BUILD_BUG_ON(sizeof(struct xen_pmu_data) > PAGE_SIZE);
 
-	if (xen_hvm_domain())
+	if (xen_hvm_domain() || (cpu != 0 && !is_xen_pmu))
 		return;
 
 	xenpmu_data = (struct xen_pmu_data *)get_zeroed_page(GFP_KERNEL);
@@ -547,7 +544,8 @@ void xen_pmu_init(int cpu)
 	per_cpu(xenpmu_shared, cpu).xenpmu_data = xenpmu_data;
 	per_cpu(xenpmu_shared, cpu).flags = 0;
 
-	if (cpu == 0) {
+	if (!is_xen_pmu) {
+		is_xen_pmu = true;
 		perf_register_guest_info_callbacks(&xen_guest_cbs);
 		xen_pmu_arch_init();
 	}
diff --git a/arch/x86/xen/pmu.h b/arch/x86/xen/pmu.h
index 0e83a160589b..65c58894fc79 100644
--- a/arch/x86/xen/pmu.h
+++ b/arch/x86/xen/pmu.h
@@ -4,6 +4,8 @@
 
 #include <xen/interface/xenpmu.h>
 
+extern bool is_xen_pmu;
+
 irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id);
 #ifdef CONFIG_XEN_HAVE_VPMU
 void xen_pmu_init(int cpu);
@@ -12,7 +14,6 @@ void xen_pmu_finish(int cpu);
 static inline void xen_pmu_init(int cpu) {}
 static inline void xen_pmu_finish(int cpu) {}
 #endif
-bool is_xen_pmu(int cpu);
 bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err);
 bool pmu_msr_write(unsigned int msr, uint32_t low, uint32_t high, int *err);
 int pmu_apic_update(uint32_t reg);
diff --git a/arch/x86/xen/smp_hvm.c b/arch/x86/xen/smp_hvm.c
index f8d39440b292..e5bd9eb42191 100644
--- a/arch/x86/xen/smp_hvm.c
+++ b/arch/x86/xen/smp_hvm.c
@@ -19,6 +19,12 @@ static void __init xen_hvm_smp_prepare_boot_cpu(void)
 	xen_vcpu_setup(0);
 
 	/*
+	 * Called again in case the kernel boots on vcpu >= MAX_VIRT_CPUS.
+	 * Refer to comments in xen_hvm_init_time_ops().
+	 */
+	xen_hvm_init_time_ops();
+
+	/*
 	 * The alternative logic (which patches the unlock/lock) runs before
 	 * the smp bootup up code is activated. Hence we need to set this up
 	 * the core kernel is being patched. Otherwise we will have only
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index 0cebe5db691d..64e6ec2c32a7 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -129,7 +129,7 @@ int xen_smp_intr_init_pv(unsigned int cpu)
 	per_cpu(xen_irq_work, cpu).irq = rc;
 	per_cpu(xen_irq_work, cpu).name = callfunc_name;
 
-	if (is_xen_pmu(cpu)) {
+	if (is_xen_pmu) {
 		pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
 		rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
 					     xen_pmu_irq_handler,
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index befbdd8b17f0..4ec6c80f7687 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -547,6 +547,11 @@ static void xen_hvm_setup_cpu_clockevents(void)
 
 void __init xen_hvm_init_time_ops(void)
 {
+	static bool hvm_time_initialized;
+
+	if (hvm_time_initialized)
+		return;
+
 	/*
 	 * vector callback is needed otherwise we cannot receive interrupts
 	 * on cpu > 0 and at this point we don't know how many cpus are
@@ -556,7 +561,22 @@ void __init xen_hvm_init_time_ops(void)
 		return;
 
 	if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
-		pr_info("Xen doesn't support pvclock on HVM, disable pv timer");
+		pr_info_once("Xen doesn't support pvclock on HVM, disable pv timer");
+		return;
+	}
+
+	/*
+	 * Only MAX_VIRT_CPUS 'vcpu_info' are embedded inside 'shared_info'.
+	 * The __this_cpu_read(xen_vcpu) is still NULL when Xen HVM guest
+	 * boots on vcpu >= MAX_VIRT_CPUS (e.g., kexec), To access
+	 * __this_cpu_read(xen_vcpu) via xen_clocksource_read() will panic.
+	 *
+	 * The xen_hvm_init_time_ops() should be called again later after
+	 * __this_cpu_read(xen_vcpu) is available.
+	 */
+	if (!__this_cpu_read(xen_vcpu)) {
+		pr_info("Delay xen_init_time_common() as kernel is running on vcpu=%d\n",
+			xen_vcpu_nr(0));
 		return;
 	}
 
@@ -568,6 +588,8 @@ void __init xen_hvm_init_time_ops(void)
 	x86_platform.calibrate_tsc = xen_tsc_khz;
 	x86_platform.get_wallclock = xen_get_wallclock;
 	x86_platform.set_wallclock = xen_set_wallclock;
+
+	hvm_time_initialized = true;
 }
 #endif