Re: [qemu-s390x] [PATCH] target/s390x/kvm: Officially require at least kernel 3.15

[David Hildenbrand]

On 13.09.19 09:46, Thomas Huth wrote:
> Since QEMU v2.10, the KVM acceleration does not work on older kernels
> anymore since the code accidentally requires the KVM_CAP_DEVICE_CTRL
> capability now - it should have been optional instead.
> Instead of fixing the bug, we asked in the ChangeLog of QEMU 2.11 - 3.0
> that people should speak up if they still need support of QEMU running
> with KVM on older kernels, but seems like nobody really complained.
> Thus let's make this official now and turn it into a proper error
> message, telling the users to use at least kernel 3.15 now.
> 
> Signed-off-by: Thomas Huth <address@hidden>
> ---
>  hw/intc/s390_flic_kvm.c | 6 ------
>  target/s390x/kvm.c      | 7 +++++++
>  2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
> index 819aa5e198..cedccba8a9 100644
> --- a/hw/intc/s390_flic_kvm.c
> +++ b/hw/intc/s390_flic_kvm.c
> @@ -589,12 +589,6 @@ static void kvm_s390_flic_realize(DeviceState *dev, 
> Error **errp)
>          goto fail;
>      }
>      flic_state->fd = -1;
> -    if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
> -        error_setg_errno(&errp_local, errno, "KVM is missing capability"
> -                         " KVM_CAP_DEVICE_CTRL");
> -        trace_flic_no_device_api(errno);
> -        goto fail;
> -    }
>  
>      cd.type = KVM_DEV_TYPE_FLIC;
>      ret = kvm_vm_ioctl(kvm_state, KVM_CREATE_DEVICE, &cd);
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index cea71ac7c3..97a662ad0e 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -316,6 +316,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      MachineClass *mc = MACHINE_GET_CLASS(ms);
>  
>      mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
> +
> +    if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
> +        error_report("KVM is missing capability KVM_CAP_DEVICE_CTRL - "
> +                     "please use kernel 3.15 or newer");
> +        return -1;
> +    }
> +
>      cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
>      cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
>      cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
> 

The tracepoint has to go as well as fat as I can see.

Apart from that, looks good to me.

-- 

Thanks,

David / dhildenb