@@ -31,7 +31,9 @@ supporting the feature or only supporting the feature under certain
configurations. For example, the `aarch64` CPU feature, which, when
disabled, enables the optional AArch32 CPU feature, is only supported
when using the KVM accelerator and when running on a host CPU type that
-supports the feature.
+supports the feature. While `aarch64` currently only works with KVM,
+it could work with TCG. CPU features that are specific to KVM are
+prefixed with "kvm-" and are described in "KVM VCPU Features".
CPU Feature Probing
===================
@@ -171,6 +173,39 @@ disabling many SVE vector lengths would be quite verbose, the `sve<N>` CPU
properties have special semantics (see "SVE CPU Property Parsing
Semantics").
+KVM VCPU Features
+=================
+
+KVM VCPU features are CPU features that are specific to KVM, such as
+paravirt features or features that enable CPU virtualization extensions.
+The features' CPU properties are only available when KVM is enabled and
+are named with the prefix "kvm-". KVM VCPU features may be probed,
+enabled, and disabled in the same way as other CPU features. Below is
+the list of KVM VCPU features and their descriptions.
+
+ kvm-no-adjvtime By default kvm-no-adjvtime is disabled. This
+ means that by default the virtual time
+ adjustment is enabled (vtime is *not not*
+ adjusted).
+
+ When virtual time adjustment is enabled each
+ time the VM transitions back to running state
+ the VCPU's virtual counter is updated to ensure
+ stopped time is not counted. This avoids time
+ jumps surprising guest OSes and applications,
+ as long as they use the virtual counter for
+ timekeeping. However it has the side effect of
+ the virtual and physical counters diverging.
+ All timekeeping based on the virtual counter
+ will appear to lag behind any timekeeping that
+ does not subtract VM stopped time. The guest
+ may resynchronize its virtual counter with
+ other time sources as needed.
+
+ Enable kvm-no-adjvtime to disable virtual time
+ adjustment, also restoring the legacy (pre-5.0)
+ behavior.
+
SVE CPU Properties
==================
@@ -1663,6 +1663,11 @@ static void machvirt_init(MachineState *machine)
}
}
+ if (vmc->kvm_no_adjvtime &&
+ object_property_find(cpuobj, "kvm-no-adjvtime", NULL)) {
+ object_property_set_bool(cpuobj, true, "kvm-no-adjvtime", NULL);
+ }
+
if (vmc->no_pmu && object_property_find(cpuobj, "pmu", NULL)) {
object_property_set_bool(cpuobj, false, "pmu", NULL);
}
@@ -2153,8 +2158,11 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 0)
static void virt_machine_4_2_options(MachineClass *mc)
{
+ VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
+
virt_machine_5_0_options(mc);
compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len);
+ vmc->kvm_no_adjvtime = true;
}
DEFINE_VIRT_MACHINE(4, 2)
@@ -109,6 +109,7 @@ typedef struct {
bool smbios_old_sys_ver;
bool no_highmem_ecam;
bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
+ bool kvm_no_adjvtime;
} VirtMachineClass;
typedef struct {
@@ -2562,6 +2562,7 @@ static void arm_max_initfn(Object *obj)
if (kvm_enabled()) {
kvm_arm_set_cpu_features_from_host(cpu);
+ kvm_arm_add_vcpu_properties(obj);
} else {
cortex_a15_initfn(obj);
@@ -2755,6 +2756,7 @@ static void arm_host_initfn(Object *obj)
if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
aarch64_add_sve_properties(obj);
}
+ kvm_arm_add_vcpu_properties(obj);
arm_cpu_post_init(obj);
}
@@ -605,6 +605,7 @@ static void aarch64_max_initfn(Object *obj)
if (kvm_enabled()) {
kvm_arm_set_cpu_features_from_host(cpu);
+ kvm_arm_add_vcpu_properties(obj);
} else {
uint64_t t;
uint32_t u;
@@ -17,6 +17,8 @@
#include "qemu/timer.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
+#include "qom/object.h"
+#include "qapi/error.h"
#include "sysemu/sysemu.h"
#include "sysemu/kvm.h"
#include "sysemu/kvm_int.h"
@@ -179,6 +181,32 @@ void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
env->features = arm_host_cpu_features.features;
}
+static bool kvm_no_adjvtime_get(Object *obj, Error **errp)
+{
+ return !ARM_CPU(obj)->kvm_adjvtime;
+}
+
+static void kvm_no_adjvtime_set(Object *obj, bool value, Error **errp)
+{
+ ARM_CPU(obj)->kvm_adjvtime = !value;
+}
+
+/* KVM VCPU properties should be prefixed with "kvm-". */
+void kvm_arm_add_vcpu_properties(Object *obj)
+{
+ if (!kvm_enabled()) {
+ return;
+ }
+
+ ARM_CPU(obj)->kvm_adjvtime = true;
+ object_property_add_bool(obj, "kvm-no-adjvtime", kvm_no_adjvtime_get,
+ kvm_no_adjvtime_set, &error_abort);
+ object_property_set_description(obj, "kvm-no-adjvtime",
+ "Set on to disable the adjustment of "
+ "the virtual counter. VM stopped time "
+ "will be counted.", &error_abort);
+}
+
bool kvm_arm_pmu_supported(CPUState *cpu)
{
KVMState *s = KVM_STATE(current_machine->accelerator);
@@ -255,6 +255,15 @@ void kvm_arm_sve_get_vls(CPUState *cs, unsigned long *map);
*/
void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu);
+/**
+ * kvm_arm_add_vcpu_properties:
+ * @obj: The CPU object to add the properties to
+ *
+ * Add all KVM specific CPU properties to the CPU object. These
+ * are the CPU properties with "kvm-" prefixed names.
+ */
+void kvm_arm_add_vcpu_properties(Object *obj);
+
/**
* kvm_arm_aarch32_supported:
* @cs: CPUState
@@ -345,6 +354,8 @@ static inline void kvm_arm_set_cpu_features_from_host(ARMCPU *cpu)
cpu->host_cpu_probe_failed = true;
}
+static inline void kvm_arm_add_vcpu_properties(Object *obj) {}
+
static inline bool kvm_arm_aarch32_supported(CPUState *cs)
{
return false;
@@ -103,6 +103,7 @@ static const char *cpu_model_advertised_features[] = {
"sve128", "sve256", "sve384", "sve512",
"sve640", "sve768", "sve896", "sve1024", "sve1152", "sve1280",
"sve1408", "sve1536", "sve1664", "sve1792", "sve1920", "sve2048",
+ "kvm-no-adjvtime",
NULL
};
@@ -428,6 +428,8 @@ static void test_query_cpu_model_expansion(const void *data)
assert_has_feature_enabled(qts, "cortex-a15", "pmu");
assert_has_not_feature(qts, "cortex-a15", "aarch64");
+ assert_has_not_feature(qts, "max", "kvm-no-adjvtime");
+
if (g_str_equal(qtest_get_arch(), "aarch64")) {
assert_has_feature_enabled(qts, "max", "aarch64");
assert_has_feature_enabled(qts, "max", "sve");
@@ -462,6 +464,8 @@ static void test_query_cpu_model_expansion_kvm(const void *data)
return;
}
+ assert_has_feature_disabled(qts, "host", "kvm-no-adjvtime");
+
if (g_str_equal(qtest_get_arch(), "aarch64")) {
bool kvm_supports_sve;
char max_name[8], name[8];
kvm-no-adjvtime is a KVM specific CPU property and a first of its kind. To accommodate it we also add kvm_arm_add_vcpu_properties() and a KVM specific CPU properties description to the CPU features document. Signed-off-by: Andrew Jones <drjones@redhat.com> --- docs/arm-cpu-features.rst | 37 +++++++++++++++++++++++++++++++++- hw/arm/virt.c | 8 ++++++++ include/hw/arm/virt.h | 1 + target/arm/cpu.c | 2 ++ target/arm/cpu64.c | 1 + target/arm/kvm.c | 28 +++++++++++++++++++++++++ target/arm/kvm_arm.h | 11 ++++++++++ target/arm/monitor.c | 1 + tests/qtest/arm-cpu-features.c | 4 ++++ 9 files changed, 92 insertions(+), 1 deletion(-)