x86/cpu/amd: Enumerate BTC_NO

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kernel / cpu / amd.c

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index c3a23c398680c63013a6658d6ccf399691331181..92d8d8d833093a7dc16b79dbdf56a4101547f7fa 100644 (file)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -914,12 +914,21 @@ static void init_amd_zn(struct cpuinfo_x86 *c)
        node_reclaim_distance = 32;
 #endif
 
-       /*
-        * Fix erratum 1076: CPB feature bit not being set in CPUID.
-        * Always set it, except when running under a hypervisor.
-        */
-       if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_CPB))
-               set_cpu_cap(c, X86_FEATURE_CPB);
+       /* Fix up CPUID bits, but only if not virtualised. */
+       if (!cpu_has(c, X86_FEATURE_HYPERVISOR)) {
+
+               /* Erratum 1076: CPB feature bit not being set in CPUID. */
+               if (!cpu_has(c, X86_FEATURE_CPB))
+                       set_cpu_cap(c, X86_FEATURE_CPB);
+
+               /*
+                * Zen3 (Fam19 model < 0x10) parts are not susceptible to
+                * Branch Type Confusion, but predate the allocation of the
+                * BTC_NO bit.
+                */
+               if (c->x86 == 0x19 && !cpu_has(c, X86_FEATURE_BTC_NO))
+                       set_cpu_cap(c, X86_FEATURE_BTC_NO);
+       }
 }
 
 static void init_amd(struct cpuinfo_x86 *c)