Re: [RFC PATCH v2 5/5] Enable the MTE support for KVM guest

[Juan Quintela <quintela@redhat.com>]

Haibo Xu <haibo.xu@linaro.org> wrote:
> Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
> ---
>  hw/arm/virt.c | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 76658b93a3..36cfdb29e9 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -79,6 +79,7 @@
>  #include "hw/virtio/virtio-iommu.h"
>  #include "hw/char/pl011.h"
>  #include "qemu/guest-random.h"
> +#include "migration/misc.h"
>  
>  #define DEFINE_VIRT_MACHINE_LATEST(major, minor, latest) \
>      static void virt_##major##_##minor##_class_init(ObjectClass *oc, \
> @@ -828,6 +829,21 @@ static void virt_powerdown_req(Notifier *n, void *opaque)
>      }
>  }
>  
> +static int virt_precopy_notify(NotifierWithReturn *n, void *data)
> +{
> +    PrecopyNotifyData *pnd = data;
> +
> +    switch (pnd->reason) {
> +    case PRECOPY_NOTIFY_SETUP:
> +        precopy_enable_metadata_migration();
> +        break;
> +    default:
> +        break;
> +    }
> +
> +    return 0;
> +}
> +
>  static void create_gpio_keys(char *fdt, DeviceState *pl061_dev,
>                               uint32_t phandle)
>  {
> @@ -1912,9 +1928,9 @@ static void machvirt_init(MachineState *machine)
>      }
>  
>      if (vms->mte && kvm_enabled()) {
> -        error_report("mach-virt: KVM does not support providing "
> -                     "MTE to the guest CPU");
> -        exit(1);
> +        /* connect migration precopy request */
> +        vms->precopy_notifier.notify = virt_precopy_notify;
> +        precopy_add_notifier(&vms->precopy_notifier);
>      }
>  
>      create_fdt(vms);

Why are you using a notifier here?
It is not enough for you just esetup at this point a variable somewhere
   "foo->mte_enabled = true"

And create a function that just does:

bool is_mte_enabled(vode)
{
        return foo->mte_enabled;
}

And just check that everywhere?

Later, Juan.