x86/paravirt: Switch functions with custom code to ALTERNATIVE

Instead of using paravirt patching for custom code sequences use
ALTERNATIVE for the functions with custom code replacements.

Instead of patching an ud2 instruction for unpopulated vector entries
into the caller site, use a simple function just calling BUG() as a
replacement.

Simplify the register defines for assembler paravirt calling, as there
isn't much usage left.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210311142319.4723-14-jgross@suse.com
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 400908d..12e2e3c 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -305,7 +305,7 @@
 .macro DEBUG_ENTRY_ASSERT_IRQS_OFF
 #ifdef CONFIG_DEBUG_ENTRY
 	pushq %rax
-	SAVE_FLAGS(CLBR_RAX)
+	SAVE_FLAGS
 	testl $X86_EFLAGS_IF, %eax
 	jz .Lokay_\@
 	ud2