On Thu, May 26, 2016 at 10:02:10AM +0200, Greg Kurz wrote: > The KVM API restricts vcpu ids to be < KVM_CAP_MAX_VCPUS. On PowerPC > targets, depending on the number of threads per core in the host and > in the guest, some topologies do generate higher vcpu ids actually. > When this happens, QEMU bails out with the following error: > > kvm_init_vcpu failed: Invalid argument > > The KVM_CREATE_VCPU ioctl has several EINVAL return paths, so it is > not possible to fully disambiguate. > > This patch adds a check in the code that computes vcpu ids, so that > we can detect the error earlier, and print a friendlier message instead > of calling KVM_CREATE_VCPU with an obviously bogus vcpu id. > > Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> include/sysemu/kvm.h | 2 ++
> kvm-all.c | 6 ++++++
> target-ppc/translate_init.c | 8 ++++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index f9f00e2e56cb..f357ccde9122 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -345,6 +345,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s);
>
> int kvm_arch_init_vcpu(CPUState *cpu);
>
> +bool kvm_vcpu_id_is_valid(int vcpu_id);
> +
> /* Returns VCPU ID to be used on KVM_CREATE_VCPU ioctl() */
> unsigned long kvm_arch_vcpu_id(CPUState *cpu);
>
> diff --git a/kvm-all.c b/kvm-all.c
> index f9ae8f9bf809..e56f38527815 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1459,6 +1459,12 @@ static int kvm_max_vcpus(KVMState *s)
> return (ret) ? ret : kvm_recommended_vcpus(s);
> }
>
> +bool kvm_vcpu_id_is_valid(int vcpu_id)
> +{
> + KVMState *s = KVM_STATE(current_machine->accelerator);
> + return vcpu_id >= 0 && vcpu_id < kvm_max_vcpus(s);
> +}
> +
> static int kvm_init(MachineState *ms)
> {
> MachineClass *mc = MACHINE_GET_CLASS(ms);
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index 954195f5e494..a003c1029d31 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -9231,6 +9231,14 @@ static void ppc_cpu_realizefn(DeviceState *dev, Error
> **errp)
> #if !defined(CONFIG_USER_ONLY)
> cpu->cpu_dt_id = (cs->cpu_index / smp_threads) * max_smt
> + (cs->cpu_index % smp_threads);
> +
> + if (kvm_enabled() && !kvm_vcpu_id_is_valid(cpu->cpu_dt_id)) {
> + error_setg(errp, "Can't create CPU with id %d in KVM",
> cpu->cpu_dt_id);
> + error_append_hint(errp, "Adjust the number of cpus to %d "
> + "or try to raise the number of threads per core\n",
> + cpu->cpu_dt_id * smp_threads / max_smt);
> + return;
> + }
> #endif
>
> if (tcg_enabled()) {
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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