svn commit: r355134 - head/sys/x86/x86

[Scott Long]

Author: scottl
Date: Wed Nov 27 19:12:32 2019
New Revision: 355134
URL: https://svnweb.freebsd.org/changeset/base/355134

Log:
  Clean up and clarify meta commentary on TAA.  Add a state to denote
  that TSX doesn't exist on the CPU.
  
  MFC after:    3 days
  Sponsored by: Intel

Modified:
  head/sys/x86/x86/cpu_machdep.c

Modified: head/sys/x86/x86/cpu_machdep.c
==============================================================================
--- head/sys/x86/x86/cpu_machdep.c      Wed Nov 27 18:52:01 2019        
(r355133)
+++ head/sys/x86/x86/cpu_machdep.c      Wed Nov 27 19:12:32 2019        
(r355134)
@@ -1180,11 +1180,15 @@ 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
@@ -1208,7 +1212,7 @@ 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;
        }
 
@@ -1216,7 +1220,7 @@ x86_taa_recalculate(void)
        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_state = 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
@@ -1323,9 +1327,11 @@ 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";
        default:
                state = "unknown";
        }
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