x86/cpuid: Enumeration for BTC_NO

BTC_NO indicates that hardware is not succeptable to Branch Type Confusion.

Zen3 CPUs don't suffer BTC.

This is part of XSA-407.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 76cb04ad64f3ab9ae785988c40655a71dde9c319)

diff --git a/tools/libxl/libxl_cpuid.c b/tools/libxl/libxl_cpuid.c
index 86c8d21555babf76bd6e9fa2d73323167789aea6..25576b4d992d943b67a16a8327a4ae3f8348328f 100644 (file)
--- a/tools/libxl/libxl_cpuid.c
+++ b/tools/libxl/libxl_cpuid.c
@@ -280,6 +280,7 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str)
         {"virt-ssbd",    0x80000008, NA, CPUID_REG_EBX, 25,  1},
         {"ssb-no",       0x80000008, NA, CPUID_REG_EBX, 26,  1},
         {"psfd",         0x80000008, NA, CPUID_REG_EBX, 28,  1},
+        {"btc-no",       0x80000008, NA, CPUID_REG_EBX, 29,  1},
 
         {"nc",           0x80000008, NA, CPUID_REG_ECX,  0,  8},
         {"apicidsize",   0x80000008, NA, CPUID_REG_ECX, 12,  4},

diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 7ebf520a71715a8c199223fb20fdd112b0a0fbbc..e5208cfa4538c85417efe05ab415e76f43202dbc 100644 (file)
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -157,7 +157,7 @@ static const char *const str_e8b[32] =
     /* [22] */                 [23] = "ppin",
     [24] = "amd-ssbd",         [25] = "virt-ssbd",
     [26] = "ssb-no",
-    [28] = "psfd",
+    [28] = "psfd",             [29] = "btc-no",
 };
 
 static const char *const str_7d0[32] =

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index 142f34af5f70892ee7c7c642d8ee9ef35db9ec9a..7409af98f6337c596e75aa67f116310a385cdfea 100644 (file)
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -822,6 +822,16 @@ static void init_amd(struct cpuinfo_x86 *c)
                        warning_add(text);
                }
                break;
+
+       case 0x19:
+               /*
+                * Zen3 (Fam19h model < 0x10) parts are not susceptible to
+                * Branch Type Confusion, but predate the allocation of the
+                * BTC_NO bit.  Fill it back in if we're not virtualised.
+                */
+               if (!cpu_has_hypervisor && !cpu_has(c, X86_FEATURE_BTC_NO))
+                       __set_bit(X86_FEATURE_BTC_NO, c->x86_capability);
+               break;
        }
 
        display_cacheinfo(c);

diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index ced0f8c2aea62f48469dd91922c84e8a6cd1aad1..9f66c715516cf04286a130520326d68630720789 100644 (file)
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -388,7 +388,7 @@ 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\n",
+    printk("  Hardware hints:%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"           : "",
@@ -403,7 +403,8 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
            (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"      : "",
-           (e8b  & cpufeat_mask(X86_FEATURE_IBRS_SAME_MODE)) ? " IBRS_SAME_MODE" : "");
+           (e8b  & cpufeat_mask(X86_FEATURE_IBRS_SAME_MODE)) ? " IBRS_SAME_MODE" : "",
+           (e8b  & cpufeat_mask(X86_FEATURE_BTC_NO))         ? " BTC_NO"         : "");
 
     /* Hardware features which need driving to mitigate issues. */
     printk("  Hardware features:%s%s%s%s%s%s%s%s%s%s%s%s\n",

diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index c5af6f03cff67964c73c4e1270e5fb4cee73cff5..746a75200ab8c36337111378f2ad1d259e9a2644 100644 (file)
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -264,6 +264,7 @@ XEN_CPUFEATURE(AMD_SSBD,      8*32+24) /*S  MSR_SPEC_CTRL.SSBD available */
 XEN_CPUFEATURE(VIRT_SSBD,     8*32+25) /*   MSR_VIRT_SPEC_CTRL.SSBD */
 XEN_CPUFEATURE(SSB_NO,        8*32+26) /*A  Hardware not vulnerable to SSB */
 XEN_CPUFEATURE(PSFD,          8*32+28) /*S  MSR_SPEC_CTRL.PSFD */
+XEN_CPUFEATURE(BTC_NO,        8*32+29) /*A  Hardware not vulnerable to Branch Type Confusion */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0.edx, word 9 */
 XEN_CPUFEATURE(AVX512_4VNNIW, 9*32+ 2) /*A  AVX512 Neural Network Instructions */