Re: [Qemu-devel] [RFC PATCH V2 3/6] target-arm: Enable KVM_ARM_VCPU_PSCI_0_2 feature when possible

[Peter Maydell]

On 1 April 2014 12:53, Pranavkumar Sawargaonkar <address@hidden> wrote:
> Latest linux kernel supports in-kernel emulation of PSCI v0.2 but
> to enable it we need to select KVM_ARM_VCPU_PSCI_0_2 feature using
> KVM_ARM_VCPU_INIT ioctl.
>
> Also, we can use KVM_ARM_VCPU_PSCI_0_2 feature for VCPU only when
> linux kernel has KVM_CAP_ARM_PSCI_0_2 capability.
>
> This patch updates kvm_arch_init_vcpu() to enable KVM_ARM_VCPU_PSCI_0_2
> feature for VCPU when KVM ARM/ARM64 has KVM_CAP_ARM_PSCI_0_2 capability.
>
> Signed-off-by: Pranavkumar Sawargaonkar <address@hidden>
> Signed-off-by: Anup Patel <address@hidden>
> ---
>  target-arm/kvm32.c |    5 ++++-
>  target-arm/kvm64.c |    5 ++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/target-arm/kvm32.c b/target-arm/kvm32.c
> index a4fde07..afeff01 100644
> --- a/target-arm/kvm32.c
> +++ b/target-arm/kvm32.c
> @@ -181,7 +181,10 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      init.target = cpu->kvm_target;
>      memset(init.features, 0, sizeof(init.features));
>      if (cpu->start_powered_off) {
> -        init.features[0] = 1 << KVM_ARM_VCPU_POWER_OFF;
> +        init.features[0] |= 1 << KVM_ARM_VCPU_POWER_OFF;
> +    }
> +    if (kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_PSCI_0_2)) {
> +        init.features[0] |= 1 << KVM_ARM_VCPU_PSCI_0_2;
>      }

I vaguely remember mentioning migration incompatibilities
last time round. You can't do this because this means that
a QEMU running on a non-0.2-aware kernel won't be able to
migrate its VM to a QEMU running on a 0.2-aware kernel.
PSCI version is probably going to need to be a CPU property;
needs more thought.

thanks
-- PMM