x86: xen: add missing prototypes

These function are all called from assembler files, or from inline
assembler, so there is no immediate need for a prototype in a header,
but if -Wmissing-prototypes is enabled, the compiler warns about them:

arch/x86/xen/efi.c:130:13: error: no previous prototype for 'xen_efi_init' [-Werror=missing-prototypes]
arch/x86/platform/pvh/enlighten.c:120:13: error: no previous prototype for 'xen_prepare_pvh' [-Werror=missing-prototypes]
arch/x86/xen/enlighten_pv.c:1233:34: error: no previous prototype for 'xen_start_kernel' [-Werror=missing-prototypes]
arch/x86/xen/irq.c:22:14: error: no previous prototype for 'xen_force_evtchn_callback' [-Werror=missing-prototypes]
arch/x86/entry/common.c:302:24: error: no previous prototype for 'xen_pv_evtchn_do_upcall' [-Werror=missing-prototypes]

Declare all of them in an appropriate header file to avoid the warnings.
For consistency, also move the asm_cpu_bringup_and_idle() declaration
out of smp_pv.c.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20230614073501.10101-3-jgross@suse.comSigned-off-by: Juergen Gross <jgross@suse.com>

arch/x86/xen/efi.c

@@ -16,6 +16,8 @@
 #include <asm/setup.h>
 #include <asm/xen/hypercall.h>
 
+#include "xen-ops.h"
+
 static efi_char16_t vendor[100] __initdata;
 
 static efi_system_table_t efi_systab_xen __initdata = {

arch/x86/xen/smp.h

@@ -2,6 +2,10 @@
 #ifndef _XEN_SMP_H
 
 #ifdef CONFIG_SMP
+
+void asm_cpu_bringup_and_idle(void);
+asmlinkage void cpu_bringup_and_idle(void);
+
 extern void xen_send_IPI_mask(const struct cpumask *mask,
 			      int vector);
 extern void xen_send_IPI_mask_allbutself(const struct cpumask *mask,

arch/x86/xen/smp_pv.c

@@ -55,7 +55,6 @@ static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
 
 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
-void asm_cpu_bringup_and_idle(void);
 
 static void cpu_bringup(void)
 {

arch/x86/xen/xen-ops.h

@@ -146,9 +146,12 @@ int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
 void xen_pin_vcpu(int cpu);
 
 void xen_emergency_restart(void);
+void xen_force_evtchn_callback(void);
+
 #ifdef CONFIG_XEN_PV
 void xen_pv_pre_suspend(void);
 void xen_pv_post_suspend(int suspend_cancelled);
+void xen_start_kernel(struct start_info *si);
 #else
 static inline void xen_pv_pre_suspend(void) {}
 static inline void xen_pv_post_suspend(int suspend_cancelled) {}

include/xen/xen.h

@@ -31,6 +31,9 @@ extern uint32_t xen_start_flags;
 
 #include <xen/interface/hvm/start_info.h>
 extern struct hvm_start_info pvh_start_info;
+void xen_prepare_pvh(void);
+struct pt_regs;
+void xen_pv_evtchn_do_upcall(struct pt_regs *regs);
 
 #ifdef CONFIG_XEN_DOM0
 #include <xen/interface/xen.h>