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authorEduardo Habkost <ehabkost@redhat.com>2017-01-16 19:11:21 -0200
committerEduardo Habkost <ehabkost@redhat.com>2017-02-27 13:23:09 -0300
commitb8d834a00fa3ed4dad7d371e1a00938a126a54a0 (patch)
tree18e354bb876bbf0c96fc8b8ea872b06c2712e737 /target/i386
parent44bd8e530661be1d22ae0f461a5c9bdbcc3847ec (diff)
i386: Reorganize and document CPUID initialization steps
CPU runnability checks and CPU model expansion have slightly different requirements. Document the steps involved in loading a CPU model and realizing a CPU, so their requirements and purpose are clearly defined. This patch doesn't change any implementation. It just add comments, rename the x86_cpu_load_features() function for clarity (so it won't be confused with x86_cpu_load_def()), and move x86_cpu_filter_features() closer to it. Message-Id: <20170116211124.29245-2-ehabkost@redhat.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Diffstat (limited to 'target/i386')
-rw-r--r--target/i386/cpu.c102
1 files changed, 71 insertions, 31 deletions
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 87affbfcd6..b614887a61 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -2059,7 +2059,7 @@ static void x86_cpu_parse_featurestr(const char *typename, char *features,
}
}
-static void x86_cpu_load_features(X86CPU *cpu, Error **errp);
+static void x86_cpu_expand_features(X86CPU *cpu, Error **errp);
static int x86_cpu_filter_features(X86CPU *cpu);
/* Check for missing features that may prevent the CPU class from
@@ -2082,9 +2082,9 @@ static void x86_cpu_class_check_missing_features(X86CPUClass *xcc,
xc = X86_CPU(object_new(object_class_get_name(OBJECT_CLASS(xcc))));
- x86_cpu_load_features(xc, &err);
+ x86_cpu_expand_features(xc, &err);
if (err) {
- /* Errors at x86_cpu_load_features should never happen,
+ /* Errors at x86_cpu_expand_features should never happen,
* but in case it does, just report the model as not
* runnable at all using the "type" property.
*/
@@ -2245,31 +2245,6 @@ static uint32_t x86_cpu_get_supported_feature_word(FeatureWord w,
return r;
}
-/*
- * Filters CPU feature words based on host availability of each feature.
- *
- * Returns: 0 if all flags are supported by the host, non-zero otherwise.
- */
-static int x86_cpu_filter_features(X86CPU *cpu)
-{
- CPUX86State *env = &cpu->env;
- FeatureWord w;
- int rv = 0;
-
- for (w = 0; w < FEATURE_WORDS; w++) {
- 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];
- if (cpu->filtered_features[w]) {
- rv = 1;
- }
- }
-
- return rv;
-}
-
static void x86_cpu_report_filtered_features(X86CPU *cpu)
{
FeatureWord w;
@@ -3093,8 +3068,47 @@ static void x86_cpu_enable_xsave_components(X86CPU *cpu)
env->features[FEAT_XSAVE_COMP_HI] = mask >> 32;
}
-/* Load CPUID data based on configured features */
-static void x86_cpu_load_features(X86CPU *cpu, Error **errp)
+/***** Steps involved on loading and filtering CPUID data
+ *
+ * When initializing and realizing a CPU object, the steps
+ * involved in setting up CPUID data are:
+ *
+ * 1) Loading CPU model definition (X86CPUDefinition). This is
+ * implemented by x86_cpu_load_def() and should be completely
+ * transparent, as it is done automatically by instance_init.
+ * No code should need to look at X86CPUDefinition structs
+ * outside instance_init.
+ *
+ * 2) CPU expansion. This is done by realize before CPUID
+ * filtering, and will make sure host/accelerator data is
+ * loaded for CPU models that depend on host capabilities
+ * (e.g. "host"). Done by x86_cpu_expand_features().
+ *
+ * 3) CPUID filtering. This initializes extra data related to
+ * CPUID, and checks if the host supports all capabilities
+ * required by the CPU. Runnability of a CPU model is
+ * determined at this step. Done by x86_cpu_filter_features().
+ *
+ * Some operations don't require all steps to be performed.
+ * More precisely:
+ *
+ * - CPU instance creation (instance_init) will run only CPU
+ * model loading. CPU expansion can't run at instance_init-time
+ * because host/accelerator data may be not available yet.
+ * - CPU realization will perform both CPU model expansion and CPUID
+ * filtering, and return an error in case one of them fails.
+ * - query-cpu-definitions needs to run all 3 steps. It needs
+ * to run CPUID filtering, as the 'unavailable-features'
+ * field is set based on the filtering results.
+ * - The query-cpu-model-expansion QMP command only needs to run
+ * CPU model loading and CPU expansion. It should not filter
+ * any CPUID data based on host capabilities.
+ */
+
+/* Expand CPU configuration data, based on configured features
+ * and host/accelerator capabilities when appropriate.
+ */
+static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
{
CPUX86State *env = &cpu->env;
FeatureWord w;
@@ -3171,6 +3185,32 @@ out:
}
}
+/*
+ * Finishes initialization of CPUID data, filters CPU feature
+ * words based on host availability of each feature.
+ *
+ * Returns: 0 if all flags are supported by the host, non-zero otherwise.
+ */
+static int x86_cpu_filter_features(X86CPU *cpu)
+{
+ CPUX86State *env = &cpu->env;
+ FeatureWord w;
+ int rv = 0;
+
+ for (w = 0; w < FEATURE_WORDS; w++) {
+ 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];
+ if (cpu->filtered_features[w]) {
+ rv = 1;
+ }
+ }
+
+ return rv;
+}
+
#define IS_INTEL_CPU(env) ((env)->cpuid_vendor1 == CPUID_VENDOR_INTEL_1 && \
(env)->cpuid_vendor2 == CPUID_VENDOR_INTEL_2 && \
(env)->cpuid_vendor3 == CPUID_VENDOR_INTEL_3)
@@ -3198,7 +3238,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
return;
}
- x86_cpu_load_features(cpu, &local_err);
+ x86_cpu_expand_features(cpu, &local_err);
if (local_err) {
goto out;
}