[Qemu-devel] [PATCH v2 2/9] i386: Add x-force-features option for testing

[Eduardo Habkost <ehabkost@redhat.com>]

Add a new option that can be used to disable feature flag
filtering.  This will allow CPU model compatibility test cases to
work without host hardware dependencies.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
Changes v1 -> v2:
* (none)
---
 target/i386/cpu.h | 6 ++++++
 target/i386/cpu.c | 8 ++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 0a96c78669..4727226a6a 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1417,6 +1417,12 @@ struct X86CPU {
 
     bool check_cpuid;
     bool enforce_cpuid;
+    /*
+     * Force features to be enabled even if the host doesn't support them.
+     * This is dangerous and should be done only for testing CPUID
+     * compatibility.
+     */
+    bool force_features;
     bool expose_kvm;
     bool expose_tcg;
     bool migratable;
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index ea52db0600..1bdb906e9f 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5179,8 +5179,11 @@ static int x86_cpu_filter_features(X86CPU *cpu)
         uint32_t host_feat =
             x86_cpu_get_supported_feature_word(w, false);
         uint32_t requested_features = env->features[w];
-        env->features[w] &= host_feat;
-        cpu->filtered_features[w] = requested_features & ~env->features[w];
+        uint32_t available_features = requested_features & host_feat;
+        if (!cpu->force_features) {
+            env->features[w] = available_features;
+        }
+        cpu->filtered_features[w] = requested_features & ~available_features;
         if (cpu->filtered_features[w]) {
             rv = 1;
         }
@@ -5909,6 +5912,7 @@ static Property x86_cpu_properties[] = {
 
     DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
     DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
+    DEFINE_PROP_BOOL("x-force-features", X86CPU, force_features, false),
     DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
     DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
     DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
-- 
2.18.0.rc1.1.g3f1ff2140