Re: [Qemu-devel] [QEMU PATCH v4 10/10] target/i386: kvm: Add nested migration blocker only when kernel lacks required capabilities

[Maran Wilson <maran.wilson@oracle.com>]

On 6/19/2019 9:21 AM, Liran Alon wrote:
> Previous commits have added support for migration of nested virtualization
> workloads. This was done by utilising two new KVM capabilities:
> KVM_CAP_NESTED_STATE and KVM_CAP_EXCEPTION_PAYLOAD. Both which are
> required in order to correctly migrate such workloads.
>
> Therefore, change code to add a migration blocker for vCPUs exposed with
> Intel VMX or AMD SVM in case one of these kernel capabilities is
> missing.
>
> Signed-off-by: Liran Alon <liran.alon@oracle.com>
> ---
>   target/i386/kvm.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 99480a52ad33..a3d0fbed3b35 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1313,9 +1313,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
>                                     !!(c->ecx & CPUID_EXT_SMX);
>       }
>   
> -    if (cpu_has_nested_virt(env) && !nested_virt_mig_blocker) {
> +    if (cpu_has_nested_virt(env) && !nested_virt_mig_blocker &&
> +        ((kvm_max_nested_state_length() <= 0) || !has_exception_payload)) {
>           error_setg(&nested_virt_mig_blocker,
> -                   "Nested virtualization does not support live migration yet");
> +                   "Kernel do not provide required capabilities for "

s/do/does/

And with that change:

Reviewed-by: Maran Wilson <maran.wilson@oracle.com>

Thanks,
-Maran


> +                   "nested virtualization migration. "
> +                   "(CAP_NESTED_STATE=%d, CAP_EXCEPTION_PAYLOAD=%d)",
> +                   kvm_max_nested_state_length() > 0,
> +                   has_exception_payload);
>           r = migrate_add_blocker(nested_virt_mig_blocker, &local_err);
>           if (local_err) {
>               error_report_err(local_err);