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From: Jung-uk Kim <jkim@FreeBSD.org>
Date: Fri, 30 Mar 2012 16:32:41 +0000 (UTC)
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Subject: svn commit: r233702 - head/sys/amd64/amd64
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Author: jkim
Date: Fri Mar 30 16:32:41 2012
New Revision: 233702
URL: http://svn.freebsd.org/changeset/base/233702

Log:
  Work around Erratum 721 for AMD Family 10h and 12h processors.
  
  "Under a highly specific and detailed set of internal timing conditions,
  the processor may incorrectly update the stack pointer after a long series
  of push and/or near-call instructions, or a long series of pop and/or
  near-return instructions.  The processor must be in 64-bit mode for this
  erratum to occur."
  
  MFC after:	3 days

Modified:
  head/sys/amd64/amd64/initcpu.c

Modified: head/sys/amd64/amd64/initcpu.c
==============================================================================
--- head/sys/amd64/amd64/initcpu.c	Fri Mar 30 15:08:09 2012	(r233701)
+++ head/sys/amd64/amd64/initcpu.c	Fri Mar 30 16:32:41 2012	(r233702)
@@ -79,6 +79,27 @@ SYSCTL_UINT(_hw, OID_AUTO, via_feature_r
 SYSCTL_UINT(_hw, OID_AUTO, via_feature_xcrypt, CTLFLAG_RD,
 	&via_feature_xcrypt, 0, "VIA xcrypt feature available in CPU");
 
+static void
+init_amd(void)
+{
+
+	/*
+	 * Work around Erratum 721 for Family 10h and 12h processors.
+	 * These processors may incorrectly update the stack pointer
+	 * after a long series of push and/or near-call instructions,
+	 * or a long series of pop and/or near-return instructions.
+	 *
+	 * http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf
+	 * http://support.amd.com/us/Processor_TechDocs/44739_12h_Rev_Gd.pdf
+	 */
+	switch (CPUID_TO_FAMILY(cpu_id)) {
+	case 0x10:
+	case 0x12:
+		wrmsr(0xc0011029, rdmsr(0xc0011029) | 1);
+		break;
+	}
+}
+
 /*
  * Initialize special VIA features
  */
@@ -135,8 +156,14 @@ initializecpu(void)
 		wrmsr(MSR_EFER, msr);
 		pg_nx = PG_NX;
 	}
-	if (cpu_vendor_id == CPU_VENDOR_CENTAUR)
+	switch (cpu_vendor_id) {
+	case CPU_VENDOR_AMD:
+		init_amd();
+		break;
+	case CPU_VENDOR_CENTAUR:
 		init_via();
+		break;
+	}
 }
 
 void