x86/xen: Make write_cr2() noinstr

vmlinux.o: warning: objtool: pv_ops[42]: native_write_cr2
vmlinux.o: warning: objtool: pv_ops[42]: xen_write_cr2
vmlinux.o: warning: objtool: exc_nmi()+0x127: call to pv_ops[42]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210624095148.563524913@infradead.org

arch/x86/include/asm/paravirt.h

@@ -140,7 +140,7 @@ static __always_inline unsigned long read_cr2(void)
 				ALT_NOT(X86_FEATURE_XENPV));
 }
 
-static inline void write_cr2(unsigned long x)
+static __always_inline void write_cr2(unsigned long x)
 {
 	PVOP_VCALL1(mmu.write_cr2, x);
 }

arch/x86/kernel/paravirt.c

@@ -223,6 +223,11 @@ static noinstr unsigned long pv_native_read_cr2(void)
 {
 	return native_read_cr2();
 }
+
+static noinstr void pv_native_write_cr2(unsigned long val)
+{
+	native_write_cr2(val);
+}
 #endif
 
 enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
@@ -304,7 +309,7 @@ struct paravirt_patch_template pv_ops = {
 
 #ifdef CONFIG_PARAVIRT_XXL
 	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(pv_native_read_cr2),
-	.mmu.write_cr2		= native_write_cr2,
+	.mmu.write_cr2		= pv_native_write_cr2,
 	.mmu.read_cr3		= __native_read_cr3,
 	.mmu.write_cr3		= native_write_cr3,
 

arch/x86/xen/mmu_pv.c

@@ -1204,7 +1204,8 @@ static void __init xen_pagetable_init(void)
 	xen_remap_memory();
 	xen_setup_mfn_list_list();
 }
-static void xen_write_cr2(unsigned long cr2)
+
+static noinstr void xen_write_cr2(unsigned long cr2)
 {
 	this_cpu_read(xen_vcpu)->arch.cr2 = cr2;
 }