On Thu, Sep 17, 2020 at 01:13:06PM +0200, Vitaly Kuznetsov wrote:
> QEMU's kvmclock device is only created when KVM PV feature bits for
> kvmclock (KVM_FEATURE_CLOCKSOURCE/KVM_FEATURE_CLOCKSOURCE2) are
> exposed to the guest. With 'kvm=off' cpu flag the device is not
> created and we don't call KVM_GET_CLOCK/KVM_SET_CLOCK upon migration.
> It was reported that without these call at least Hyper-V TSC page
> clocksouce (which can be enabled independently) gets broken after
> migration.
>
> Switch to creating kvmclock QEMU device unconditionally, it seems
> to always make sense to call KVM_GET_CLOCK/KVM_SET_CLOCK on migration.
> Use KVM_CAP_ADJUST_CLOCK check instead of CPUID feature bits.
>
> Reported-by: Antoine Damhet <antoine.dam...@blade-group.com>
> Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
> ---
> hw/i386/kvm/clock.c | 6 +-----
> target/i386/kvm.c | 5 +++++
> target/i386/kvm_i386.h | 1 +
> 3 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> index 64283358f91d..526c9ea5172b 100644
> --- a/hw/i386/kvm/clock.c
> +++ b/hw/i386/kvm/clock.c
> @@ -330,11 +330,7 @@ static const TypeInfo kvmclock_info = {
> /* Note: Must be called after VCPU initialization. */
> void kvmclock_create(void)
> {
> - X86CPU *cpu = X86_CPU(first_cpu);
> -
> - if (kvm_enabled() &&
> - cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> - (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
> + if (kvm_enabled() && kvm_has_adjust_clock()) {
Shouldn't the old check used when machine type <= 5.1 in order to avoid
migration incompatibility ?
> sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL);
> }
> }
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 4a8b3a41c1bc..20b31b65307b 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -143,6 +143,11 @@ bool kvm_has_adjust_clock_stable(void)
> return (ret == KVM_CLOCK_TSC_STABLE);
> }
>
> +bool kvm_has_adjust_clock(void)
> +{
> + return kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK);
> +}
> +
> bool kvm_has_exception_payload(void)
> {
> return has_exception_payload;
> diff --git a/target/i386/kvm_i386.h b/target/i386/kvm_i386.h
> index 064b8798a26c..0fce4e51d2d6 100644
> --- a/target/i386/kvm_i386.h
> +++ b/target/i386/kvm_i386.h
> @@ -34,6 +34,7 @@
>
> bool kvm_allows_irq0_override(void);
> bool kvm_has_smm(void);
> +bool kvm_has_adjust_clock(void);
> bool kvm_has_adjust_clock_stable(void);
> bool kvm_has_exception_payload(void);
> void kvm_synchronize_all_tsc(void);
> --
> 2.25.4
>
>
--
Antoine 'xdbob' Damhet
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