x86/xen: Make set_debugreg() noinstr

vmlinux.o: warning: objtool: pv_ops[2]: xen_set_debugreg
vmlinux.o: warning: objtool: pv_ops[2]: native_set_debugreg
vmlinux.o: warning: objtool: exc_debug()+0x3b: call to pv_ops[2]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Peter Zijlstra

arch/x86/include/asm/paravirt.h

@@ -118,7 +118,7 @@ static __always_inline unsigned long paravirt_get_debugreg(int reg)
 	return PVOP_CALL1(unsigned long, cpu.get_debugreg, reg);
 }
 #define get_debugreg(var, reg) var = paravirt_get_debugreg(reg)
-static inline void set_debugreg(unsigned long val, int reg)
+static __always_inline void set_debugreg(unsigned long val, int reg)
 {
 	PVOP_VCALL2(cpu.set_debugreg, reg, val);
 }

arch/x86/include/asm/xen/hypercall.h

@@ -308,7 +308,7 @@ HYPERVISOR_platform_op(struct xen_platform_op *op)
 	return _hypercall1(int, platform_op, op);
 }
 
-static inline int
+static __always_inline int
 HYPERVISOR_set_debugreg(int reg, unsigned long value)
 {
 	return _hypercall2(int, set_debugreg, reg, value);

arch/x86/kernel/paravirt.c

@@ -233,6 +233,11 @@ static noinstr unsigned long pv_native_get_debugreg(int regno)
 {
 	return native_get_debugreg(regno);
 }
+
+static noinstr void pv_native_set_debugreg(int regno, unsigned long val)
+{
+	native_set_debugreg(regno, val);
+}
 #endif
 
 enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
@@ -260,7 +265,7 @@ struct paravirt_patch_template pv_ops = {
 #ifdef CONFIG_PARAVIRT_XXL
 	.cpu.cpuid		= native_cpuid,
 	.cpu.get_debugreg	= pv_native_get_debugreg,
-	.cpu.set_debugreg	= native_set_debugreg,
+	.cpu.set_debugreg	= pv_native_set_debugreg,
 	.cpu.read_cr0		= native_read_cr0,
 	.cpu.write_cr0		= native_write_cr0,
 	.cpu.write_cr4		= native_write_cr4,
@@ -386,8 +391,6 @@ struct paravirt_patch_template pv_ops = {
 };
 
 #ifdef CONFIG_PARAVIRT_XXL
-/* At this point, native_get/set_debugreg has real function entries */
-NOKPROBE_SYMBOL(native_set_debugreg);
 NOKPROBE_SYMBOL(native_load_idt);
 
 void (*paravirt_iret)(void) = native_iret;

arch/x86/xen/enlighten_pv.c

@@ -311,7 +311,7 @@ static void __init xen_init_capabilities(void)
 	}
 }
 
-static void xen_set_debugreg(int reg, unsigned long val)
+static noinstr void xen_set_debugreg(int reg, unsigned long val)
 {
 	HYPERVISOR_set_debugreg(reg, val);
 }