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From 98145bfcdcee809e370d65eb3a97a9529670ec06 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 22 Nov 2019 11:53:40 +0000
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Subject: [PATCH 07/16] target/i386: introduce generic feature dependency
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 mechanism
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <20191122115348.25000-8-pbonzini@redhat.com>
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Patchwork-id: 92610
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O-Subject: [RHEL8.2/rhel qemu-kvm PATCH 07/15] target/i386: introduce generic feature dependency mechanism
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Bugzilla: 1689270
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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RH-Acked-by: Maxim Levitsky <mlevitsk@redhat.com>
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Sometimes a CPU feature does not make sense unless another is
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present.  In the case of VMX features, KVM does not even allow
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setting the VMX controls to some invalid combinations.
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Therefore, this patch adds a generic mechanism that looks for bits
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that the user explicitly cleared, and uses them to remove other bits
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from the expanded CPU definition.  If these dependent bits were also
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explicitly *set* by the user, this will be a warning for "-cpu check"
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and an error for "-cpu enforce".  If not, then the dependent bits are
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cleared silently, for convenience.
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With VMX features, this will be used so that for example
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"-cpu host,-rdrand" will also hide support for RDRAND exiting.
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 99e24dbdaa682c7b9d0bb5b463638c585bcee1c3)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 target/i386/cpu.c | 72 ++++++++++++++++++++++++++++++++++++-------------------
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 1 file changed, 48 insertions(+), 24 deletions(-)
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diff --git a/target/i386/cpu.c b/target/i386/cpu.c
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index b06ce9d..a7360b3 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -797,10 +797,6 @@ typedef struct FeatureWordInfo {
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         /* If type==MSR_FEATURE_WORD */
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         struct {
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             uint32_t index;
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-            struct {   /*CPUID that enumerate this MSR*/
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-                FeatureWord cpuid_class;
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-                uint32_t    cpuid_flag;
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-            } cpuid_dep;
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         } msr;
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     };
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     uint32_t tcg_features; /* Feature flags supported by TCG */
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@@ -1157,10 +1153,6 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
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         },
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         .msr = {
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             .index = MSR_IA32_ARCH_CAPABILITIES,
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-            .cpuid_dep = {
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-                FEAT_7_0_EDX,
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-                CPUID_7_0_EDX_ARCH_CAPABILITIES
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-            }
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         },
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     },
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     [FEAT_CORE_CAPABILITY] = {
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@@ -1177,14 +1169,30 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
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         },
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         .msr = {
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             .index = MSR_IA32_CORE_CAPABILITY,
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-            .cpuid_dep = {
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-                FEAT_7_0_EDX,
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-                CPUID_7_0_EDX_CORE_CAPABILITY,
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-            },
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         },
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     },
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 };
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+typedef struct FeatureMask {
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+    FeatureWord index;
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+    uint32_t mask;
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+} FeatureMask;
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+
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+typedef struct FeatureDep {
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+    FeatureMask from, to;
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+} FeatureDep;
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+
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+static FeatureDep feature_dependencies[] = {
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+    {
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+        .from = { FEAT_7_0_EDX,             CPUID_7_0_EDX_ARCH_CAPABILITIES },
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+        .to = { FEAT_ARCH_CAPABILITIES,     ~0u },
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+    },
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+    {
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+        .from = { FEAT_7_0_EDX,             CPUID_7_0_EDX_CORE_CAPABILITY },
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+        .to = { FEAT_CORE_CAPABILITY,       ~0u },
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+    },
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+};
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+
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 typedef struct X86RegisterInfo32 {
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     /* Name of register */
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     const char *name;
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@@ -4967,9 +4975,26 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
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 {
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     CPUX86State *env = &cpu->env;
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     FeatureWord w;
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+    int i;
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     GList *l;
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     Error *local_err = NULL;
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+    for (l = plus_features; l; l = l->next) {
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+        const char *prop = l->data;
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+        object_property_set_bool(OBJECT(cpu), true, prop, &local_err);
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+        if (local_err) {
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+            goto out;
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+        }
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+    }
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+
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+    for (l = minus_features; l; l = l->next) {
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+        const char *prop = l->data;
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+        object_property_set_bool(OBJECT(cpu), false, prop, &local_err);
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+        if (local_err) {
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+            goto out;
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+        }
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+    }
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+
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     /*TODO: Now cpu->max_features doesn't overwrite features
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      * set using QOM properties, and we can convert
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      * plus_features & minus_features to global properties
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@@ -4987,19 +5012,18 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
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         }
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     }
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-    for (l = plus_features; l; l = l->next) {
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-        const char *prop = l->data;
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-        object_property_set_bool(OBJECT(cpu), true, prop, &local_err);
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-        if (local_err) {
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-            goto out;
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-        }
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-    }
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+    for (i = 0; i < ARRAY_SIZE(feature_dependencies); i++) {
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+        FeatureDep *d = &feature_dependencies[i];
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+        if (!(env->features[d->from.index] & d->from.mask)) {
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+            uint32_t unavailable_features = env->features[d->to.index] & d->to.mask;
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-    for (l = minus_features; l; l = l->next) {
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-        const char *prop = l->data;
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-        object_property_set_bool(OBJECT(cpu), false, prop, &local_err);
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-        if (local_err) {
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-            goto out;
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+            /* Not an error unless the dependent feature was added explicitly.  */
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+            mark_unavailable_features(cpu, d->to.index,
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+                                      unavailable_features & env->user_features[d->to.index],
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+                                      "This feature depends on other features that were not requested");
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+
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+            env->user_features[d->to.index] |= unavailable_features;
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+            env->features[d->to.index] &= ~unavailable_features;
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         }
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     }
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-- 
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1.8.3.1
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