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Date:      Fri, 13 Dec 2019 05:29:27 +0000 (UTC)
From:      Scott Long <scottl@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r355698 - stable/12/sys/x86/x86
Message-ID:  <201912130529.xBD5TRCD059690@repo.freebsd.org>
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Author: scottl
Date: Fri Dec 13 05:29:26 2019
New Revision: 355698
URL: https://svnweb.freebsd.org/changeset/base/355698

Log:
  Merge r355134,355375,355589
  
  Clean up and clarify meta commentary on TAA.  Add a state to denote
  that TSX doesn't exist on the CPU.
  
  x86: Add missed break to TAA status sysctl
  
  Fix the TAA state machine to do the right thing when the TAA
  migitation is available in microcode and the operator has set
  the sysctl to automatic mode.
  
  Sponsored by:	Intel

Modified:
  stable/12/sys/x86/x86/cpu_machdep.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/x86/x86/cpu_machdep.c
==============================================================================
--- stable/12/sys/x86/x86/cpu_machdep.c	Fri Dec 13 05:13:25 2019	(r355697)
+++ stable/12/sys/x86/x86/cpu_machdep.c	Fri Dec 13 05:29:26 2019	(r355698)
@@ -1164,11 +1164,15 @@ SYSCTL_PROC(_hw, OID_AUTO, mds_disable, CTLTYPE_INT |
 int x86_taa_enable;
 int x86_taa_state;
 enum {
-	TAA_NONE	= 0,
-	TAA_TSX_DISABLE	= 1,
-	TAA_VERW	= 2,
-	TAA_AUTO	= 3,
-	TAA_TAA_NO	= 4
+	TAA_NONE	= 0,	/* No mitigation enabled */
+	TAA_TSX_DISABLE	= 1,	/* Disable TSX via MSR */
+	TAA_VERW	= 2,	/* Use VERW mitigation */
+	TAA_AUTO	= 3,	/* Automatically select the mitigation */
+
+	/* The states below are not selectable by the operator */
+
+	TAA_TAA_UC	= 4,	/* Mitigation present in microcode */
+	TAA_NOT_PRESENT	= 5	/* TSX is not present */
 };
 
 static void
@@ -1192,15 +1196,14 @@ x86_taa_recalculate(void)
 	if ((cpu_stdext_feature & CPUID_STDEXT_HLE) == 0 ||
 	    (cpu_stdext_feature & CPUID_STDEXT_RTM) == 0) {
 		/* TSX is not present */
-		x86_taa_state = 0;
+		x86_taa_state = TAA_NOT_PRESENT;
 		return;
 	}
 
 	/* Check to see what mitigation options the CPU gives us */
 	if (cpu_ia32_arch_caps & IA32_ARCH_CAP_TAA_NO) {
 		/* CPU is not suseptible to TAA */
-		taa_need = TAA_NONE;
-		taa_state = TAA_TAA_NO;
+		taa_need = TAA_TAA_UC;
 	} else if (cpu_ia32_arch_caps & IA32_ARCH_CAP_TSX_CTRL) {
 		/*
 		 * CPU can turn off TSX.  This is the next best option
@@ -1307,8 +1310,11 @@ sysctl_taa_state_handler(SYSCTL_HANDLER_ARGS)
 	case TAA_VERW:
 		state = "VERW";
 		break;
-	case TAA_TAA_NO:
-		state = "Not vulnerable";
+	case TAA_TAA_UC:
+		state = "Mitigated in microcode";
+		break;
+	case TAA_NOT_PRESENT:
+		state = "TSX not present";
 		break;
 	default:
 		state = "unknown";

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