svn commit: r338683 - head/sys/amd64/amd64

[Mateusz Guzik]

Author: mjg
Date: Fri Sep 14 15:29:35 2018
New Revision: 338683
URL: https://svnweb.freebsd.org/changeset/base/338683

Log:
  amd64: implement pagezero_erms
  
  Intel docs claim such a memset (rep stosb + 4096 bytes) is
  special-cased by microarchs. They also switched Linux to use
  it for this purpose.
  
  Approved by:	re (gjb)

Modified:
  head/sys/amd64/amd64/machdep.c
  head/sys/amd64/amd64/support.S

Modified: head/sys/amd64/amd64/machdep.c
==============================================================================
--- head/sys/amd64/amd64/machdep.c	Fri Sep 14 15:15:16 2018	(r338682)
+++ head/sys/amd64/amd64/machdep.c	Fri Sep 14 15:29:35 2018	(r338683)
@@ -2693,3 +2693,12 @@ DEFINE_IFUNC(, void *, memcpy, (void * _Nonnull, const
 	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
 		memcpy_erms : memcpy_std);
 }
+
+void	pagezero_std(void *addr);
+void	pagezero_erms(void *addr);
+DEFINE_IFUNC(, void , pagezero, (void *), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		pagezero_erms : pagezero_std);
+}

Modified: head/sys/amd64/amd64/support.S
==============================================================================
--- head/sys/amd64/amd64/support.S	Fri Sep 14 15:15:16 2018	(r338682)
+++ head/sys/amd64/amd64/support.S	Fri Sep 14 15:29:35 2018	(r338683)
@@ -41,7 +41,7 @@
 	.text
 
 /* Address: %rdi */
-ENTRY(pagezero)
+ENTRY(pagezero_std)
 	PUSH_FRAME_POINTER
 	movq	$PAGE_SIZE/8,%rcx
 	xorl	%eax,%eax
@@ -49,7 +49,17 @@ ENTRY(pagezero)
 	stosq
 	POP_FRAME_POINTER
 	ret
-END(pagezero)
+END(pagezero_std)
+
+ENTRY(pagezero_erms)
+	PUSH_FRAME_POINTER
+	movq	$PAGE_SIZE,%rcx
+	xorl	%eax,%eax
+	rep
+	stosb
+	POP_FRAME_POINTER
+	ret
+END(pagezero_erms)
 
 /*
  * pagecopy(%rdi=from, %rsi=to)