[Qemu-devel] [PATCH v6 3/3] x86: define a new MSR based feature word -- FEATURE_WORDS_ARCH_CAPABILITIES

[Robert Hoo <robert.hu@linux.intel.com>]

Note RSBA is specially treated -- no matter host support it or not, qemu
pretends it is supported.

Changes in v6: filter out MSR features whose dependent CPUID enumeration is not
there.

Signed-off-by: Robert Hoo <robert.hu@linux.intel.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
---
 target/i386/cpu.c | 31 ++++++++++++++++++++++++++++++-
 target/i386/cpu.h |  8 ++++++++
 target/i386/kvm.c | 11 +++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 0de21fa..6371722 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1141,6 +1141,27 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         },
         .tcg_features = ~0U,
     },
+    /*Below are MSR exposed features*/
+    [FEAT_ARCH_CAPABILITIES] = {
+        .type = MSR_FEATURE_WORD,
+        .feat_names = {
+            "rdctl-no", "ibrs-all", "rsba", "skip-l1dfl-vmentry",
+            "ssb-no", NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+            NULL, NULL, NULL, NULL,
+        },
+        .msr = {
+            .index = MSR_IA32_ARCH_CAPABILITIES,
+            .cpuid_dep = {
+                FEAT_7_0_EDX,
+                CPUID_7_0_EDX_ARCH_CAPABILITIES
+            }
+        },
+    },
 };
 
 typedef struct X86RegisterInfo32 {
@@ -3696,7 +3717,15 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
                                                         wi->cpuid.reg);
             break;
         case MSR_FEATURE_WORD:
-            r = kvm_arch_get_supported_msr_feature(kvm_state, wi->msr.index);
+            /* Special case:
+             * No matter host status, IA32_ARCH_CAPABILITIES.RSBA [bit 2]
+             * is always supported in guest.
+             */
+            if (wi->msr.index == MSR_IA32_ARCH_CAPABILITIES) {
+                r = MSR_ARCH_CAP_RSBA;
+            }
+            r |= kvm_arch_get_supported_msr_feature(kvm_state,
+                        wi->msr.index);
             break;
         }
     } else if (hvf_enabled()) {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index dd3de97..ff1ae32 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -507,6 +507,7 @@ typedef enum FeatureWord {
     FEAT_XSAVE_COMP_LO, /* CPUID[EAX=0xd,ECX=0].EAX */
     FEAT_XSAVE_COMP_HI, /* CPUID[EAX=0xd,ECX=0].EDX */
     MSR_FEATURE_WORD_BEGIN, /* Define MSR feature words below */
+    FEAT_ARCH_CAPABILITIES = MSR_FEATURE_WORD_BEGIN,
     FEATURE_WORDS,
 } FeatureWord;
 
@@ -735,6 +736,13 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
 #define CPUID_TOPOLOGY_LEVEL_SMT      (1U << 8)
 #define CPUID_TOPOLOGY_LEVEL_CORE     (2U << 8)
 
+/* MSR Feature Bits */
+#define MSR_ARCH_CAP_RDCL_NO    (1U << 0)
+#define MSR_ARCH_CAP_IBRS_ALL   (1U << 1)
+#define MSR_ARCH_CAP_RSBA       (1U << 2)
+#define MSR_ARCH_CAP_SKIP_L1DFL_VMENTRY (1U << 3)
+#define MSR_ARCH_CAP_SSB_NO     (1U << 4)
+
 #ifndef HYPERV_SPINLOCK_NEVER_RETRY
 #define HYPERV_SPINLOCK_NEVER_RETRY             0xFFFFFFFF
 #endif
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 161fc38..796a049 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1975,6 +1975,17 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
     }
 #endif
 
+    /* If host supports feature MSR, write down. */
+    if (kvm_feature_msrs) {
+        int i;
+        for (i = 0; i < kvm_feature_msrs->nmsrs; i++)
+            if (kvm_feature_msrs->indices[i] == MSR_IA32_ARCH_CAPABILITIES) {
+                kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
+                              env->features[FEAT_ARCH_CAPABILITIES]);
+                break;
+            }
+    }
+
     /*
      * The following MSRs have side effects on the guest or are too heavy
      * for normal writeback. Limit them to reset or full state updates.
-- 
1.8.3.1