target/arm/cpu: Add the kvm-no-adjvtime CPU property
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>
Message-id: 20200120101023.16030-7-drjones@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/docs/arm-cpu-features.rst b/docs/arm-cpu-features.rst
index 9b537a7..dbf3b7c 100644
--- a/docs/arm-cpu-features.rst
+++ b/docs/arm-cpu-features.rst
@@ -31,7 +31,9 @@
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 @@
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
==================
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 91d4b83..f788fe2 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1663,6 +1663,11 @@
}
}
+ 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 @@
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)
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 38f0c33..71508bf 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -109,6 +109,7 @@
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 {
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 06907b3..f86e71a 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -2551,6 +2551,7 @@
if (kvm_enabled()) {
kvm_arm_set_cpu_features_from_host(cpu);
+ kvm_arm_add_vcpu_properties(obj);
} else {
cortex_a15_initfn(obj);
@@ -2743,6 +2744,7 @@
if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
aarch64_add_sve_properties(obj);
}
+ kvm_arm_add_vcpu_properties(obj);
arm_cpu_post_init(obj);
}
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 61fd0ad..2d97bf4 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -605,6 +605,7 @@
if (kvm_enabled()) {
kvm_arm_set_cpu_features_from_host(cpu);
+ kvm_arm_add_vcpu_properties(obj);
} else {
uint64_t t;
uint32_t u;
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index e36ab0b..85860e6 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -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 @@
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)
{
return kvm_check_extension(cpu->kvm_state, KVM_CAP_ARM_PMU_V3);
diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index 01a9a18..ae9e075 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -256,6 +256,15 @@
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 @@
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;
diff --git a/target/arm/monitor.c b/target/arm/monitor.c
index fa054f8..9725dff 100644
--- a/target/arm/monitor.c
+++ b/target/arm/monitor.c
@@ -103,6 +103,7 @@
"sve128", "sve256", "sve384", "sve512",
"sve640", "sve768", "sve896", "sve1024", "sve1152", "sve1280",
"sve1408", "sve1536", "sve1664", "sve1792", "sve1920", "sve2048",
+ "kvm-no-adjvtime",
NULL
};
diff --git a/tests/qtest/arm-cpu-features.c b/tests/qtest/arm-cpu-features.c
index a039e3c..4692173 100644
--- a/tests/qtest/arm-cpu-features.c
+++ b/tests/qtest/arm-cpu-features.c
@@ -428,6 +428,8 @@
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 @@
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];
