[PATCH] x86-64: use RIP-relative calls for paravirt indirect ones

[PATCH] x86-64: use RIP-relative calls for paravirt indirect ones

[Jan Beulich]

This saves one insn byte per instance, summing up to a savings of over
4k in my (stripped down) configuration. No variant of to be patched in
replacement code relies on the one byte larger size.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
 arch/x86/include/asm/paravirt_types.h |    6 ++++++
 1 file changed, 6 insertions(+)

--- 4.18-rc2/arch/x86/include/asm/paravirt_types.h
+++ 4.18-rc2-x86_64-pvops-call-RIPrel/arch/x86/include/asm/paravirt_types.h
@@ -393,9 +393,15 @@ int paravirt_disable_iospace(void);
  * offset into the paravirt_patch_template structure, and can therefore be
  * freely converted back into a structure offset.
  */
+#ifdef CONFIG_X86_32
 #define PARAVIRT_CALL					\
 	ANNOTATE_RETPOLINE_SAFE				\
 	"call *%c[paravirt_opptr];"
+#else
+#define PARAVIRT_CALL					\
+	ANNOTATE_RETPOLINE_SAFE				\
+	"call *%c[paravirt_opptr](%%rip);"
+#endif
 
 /*
  * These macros are intended to wrap calls through one of the paravirt

Re: [PATCH] x86-64: use RIP-relative calls for paravirt indirect ones

[Juergen Gross]

On 25/06/18 12:29, Jan Beulich wrote:
> This saves one insn byte per instance, summing up to a savings of over
> 4k in my (stripped down) configuration. No variant of to be patched in
> replacement code relies on the one byte larger size.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen