x86/spec-ctrl: Enumeration for PBRSB_NO

The PBRSB_NO bit indicates that the CPU is not vulnerable to the Post-Barrier
RSB speculative vulnerability.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/include/asm/msr-index.h

@@ -84,6 +84,7 @@
 #define  ARCH_CAPS_FB_CLEAR_CTRL            (_AC(1, ULL) << 18)
 #define  ARCH_CAPS_RRSBA                    (_AC(1, ULL) << 19)
 #define  ARCH_CAPS_BHI_NO                   (_AC(1, ULL) << 20)
+#define  ARCH_CAPS_PBRSB_NO                 (_AC(1, ULL) << 24)
 
 #define MSR_FLUSH_CMD                       0x0000010b
 #define  FLUSH_CMD_L1D                      (_AC(1, ULL) <<  0)

xen/arch/x86/msr.c

@@ -74,7 +74,8 @@ static void __init calculate_host_policy(void)
          ARCH_CAPS_SKIP_L1DFL | ARCH_CAPS_SSB_NO | ARCH_CAPS_MDS_NO |
          ARCH_CAPS_IF_PSCHANGE_MC_NO | ARCH_CAPS_TSX_CTRL | ARCH_CAPS_TAA_NO |
          ARCH_CAPS_SBDR_SSDP_NO | ARCH_CAPS_FBSDP_NO | ARCH_CAPS_PSDP_NO |
-         ARCH_CAPS_FB_CLEAR | ARCH_CAPS_RRSBA | ARCH_CAPS_BHI_NO);
+         ARCH_CAPS_FB_CLEAR | ARCH_CAPS_RRSBA | ARCH_CAPS_BHI_NO |
+         ARCH_CAPS_PBRSB_NO);
 }
 
 static void __init calculate_pv_max_policy(void)
@@ -166,7 +167,7 @@ int init_domain_msr_policy(struct domain *d)
              ARCH_CAPS_SSB_NO | ARCH_CAPS_MDS_NO | ARCH_CAPS_IF_PSCHANGE_MC_NO |
              ARCH_CAPS_TAA_NO | ARCH_CAPS_SBDR_SSDP_NO | ARCH_CAPS_FBSDP_NO |
              ARCH_CAPS_PSDP_NO | ARCH_CAPS_FB_CLEAR | ARCH_CAPS_RRSBA |
-             ARCH_CAPS_BHI_NO);
+             ARCH_CAPS_BHI_NO | ARCH_CAPS_PBRSB_NO);
     }
 
     d->arch.msr = mp;

xen/arch/x86/spec_ctrl.c

@@ -419,7 +419,7 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
      * Hardware read-only information, stating immunity to certain issues, or
      * suggestions of which mitigation to use.
      */
-    printk("  Hardware hints:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s\n",
+    printk("  Hardware hints:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s\n",
            (caps & ARCH_CAPS_RDCL_NO)                        ? " RDCL_NO"        : "",
            (caps & ARCH_CAPS_IBRS_ALL)                       ? " IBRS_ALL"       : "",
            (caps & ARCH_CAPS_RSBA)                           ? " RSBA"           : "",
@@ -431,6 +431,7 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
            (caps & ARCH_CAPS_SBDR_SSDP_NO)                   ? " SBDR_SSDP_NO"   : "",
            (caps & ARCH_CAPS_FBSDP_NO)                       ? " FBSDP_NO"       : "",
            (caps & ARCH_CAPS_PSDP_NO)                        ? " PSDP_NO"        : "",
+           (caps & ARCH_CAPS_PBRSB_NO)                       ? " PBRSB_NO"       : "",
            (e8b  & cpufeat_mask(X86_FEATURE_IBRS_ALWAYS))    ? " IBRS_ALWAYS"    : "",
            (e8b  & cpufeat_mask(X86_FEATURE_STIBP_ALWAYS))   ? " STIBP_ALWAYS"   : "",
            (e8b  & cpufeat_mask(X86_FEATURE_IBRS_FAST))      ? " IBRS_FAST"      : "",