xen/pvhvm: run xen_vcpu_setup() for the boot CPU

Historically we didn't call VCPUOP_register_vcpu_info for CPU0 for
PVHVM guests (while we had it for PV and ARM guests). This is usually
fine as we can use vcpu info in the shared_info page but when we try
booting on a vCPU with Xen's vCPU id > 31 (e.g. when we try to kdump
after crashing on this CPU) we're not able to boot.

Switch to always doing VCPUOP_register_vcpu_info for the boot CPU.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

arch/x86/xen/enlighten.c

@@ -184,7 +184,7 @@ static void clamp_max_cpus(void)
 #endif
 }
 
-static void xen_vcpu_setup(int cpu)
+void xen_vcpu_setup(int cpu)
 {
 	struct vcpu_register_vcpu_info info;
 	int err;

arch/x86/xen/smp.c

@@ -322,6 +322,13 @@ static void __init xen_smp_prepare_boot_cpu(void)
 		xen_filter_cpu_maps();
 		xen_setup_vcpu_info_placement();
 	}
+
+	/*
+	 * Setup vcpu_info for boot CPU.
+	 */
+	if (xen_hvm_domain())
+		xen_vcpu_setup(0);
+
 	/*
 	 * The alternative logic (which patches the unlock/lock) runs before
 	 * the smp bootup up code is activated. Hence we need to set this up

arch/x86/xen/xen-ops.h

@@ -76,6 +76,7 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id);
 
 bool xen_vcpu_stolen(int vcpu);
 
+void xen_vcpu_setup(int cpu);
 void xen_setup_vcpu_info_placement(void);
 
 #ifdef CONFIG_SMP