Commit dea101a1 authored by Andrew Jones's avatar Andrew Jones Committed by Peter Maydell
Browse files

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: default avatarAndrew Jones <drjones@redhat.com>
Message-id: 20200120101023.16030-7-drjones@redhat.com
Reviewed-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
parent e5ac4200

docs/arm-cpu-features.rst

+36 −1
Original line number Diff line number Diff line
@@ -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

==================

hw/arm/virt.c

+8 −0
Original line number Diff line number Diff line
@@ -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)

include/hw/arm/virt.h

+1 −0
Original line number Diff line number Diff line
@@ -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 {

target/arm/cpu.c

+2 −0
Original line number Diff line number Diff line
@@ -2551,6 +2551,7 @@ 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);
@@ -2743,6 +2744,7 @@ 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);

}

target/arm/cpu64.c

+1 −0
Original line number Diff line number Diff line
@@ -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;