Re: [PATCH v3 01/26] s390/stattrib: Add Error** argument to set_migrationmode() handler

[Avihai Horon]

On 04/03/2024 14:28, Cédric Le Goater wrote:
> External email: Use caution opening links or attachments
>
>
> This will prepare ground for futur changes adding an Error** argument
> to the save_setup() handler. We need to make sure that on failure,
> set_migrationmode() always sets a new error. See the Rules section in
> qapi/error.h.
>
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
> Cc: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
>   include/hw/s390x/storage-attributes.h |  2 +-
>   hw/s390x/s390-stattrib-kvm.c          | 12 ++++++++++--
>   hw/s390x/s390-stattrib.c              | 14 +++++++++-----
>   3 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/include/hw/s390x/storage-attributes.h 
> b/include/hw/s390x/storage-attributes.h
> index 
> 5239eb538c1b087797867a247abfc14551af6a4d..8921a04d514bf64a3113255ee10ed33fc598ae06
>  100644
> --- a/include/hw/s390x/storage-attributes.h
> +++ b/include/hw/s390x/storage-attributes.h
> @@ -39,7 +39,7 @@ struct S390StAttribClass {
>       int (*set_stattr)(S390StAttribState *sa, uint64_t start_gfn,
>                         uint32_t count, uint8_t *values);
>       void (*synchronize)(S390StAttribState *sa);
> -    int (*set_migrationmode)(S390StAttribState *sa, bool value);
> +    int (*set_migrationmode)(S390StAttribState *sa, bool value, Error **errp);
>       int (*get_active)(S390StAttribState *sa);
>       long long (*get_dirtycount)(S390StAttribState *sa);
>   };
> diff --git a/hw/s390x/s390-stattrib-kvm.c b/hw/s390x/s390-stattrib-kvm.c
> index 
> 24cd01382e2d74d62c2d7e980eb6aca1077d893d..357cea2c987213b867c81b0e258f7d0c293fe665
>  100644
> --- a/hw/s390x/s390-stattrib-kvm.c
> +++ b/hw/s390x/s390-stattrib-kvm.c
> @@ -17,6 +17,7 @@
>   #include "sysemu/kvm.h"
>   #include "exec/ram_addr.h"
>   #include "kvm/kvm_s390x.h"
> +#include "qapi/error.h"
>
>   Object *kvm_s390_stattrib_create(void)
>   {
> @@ -137,14 +138,21 @@ static void 
> kvm_s390_stattrib_synchronize(S390StAttribState *sa)
>       }
>   }
>
> -static int kvm_s390_stattrib_set_migrationmode(S390StAttribState *sa, bool val)
> +static int kvm_s390_stattrib_set_migrationmode(S390StAttribState *sa, bool val,
> +                                               Error **errp)
>   {
>       struct kvm_device_attr attr = {
>           .group = KVM_S390_VM_MIGRATION,
>           .attr = val,
>           .addr = 0,
>       };
> -    return kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attr);
> +    int r;
> +
> +    r = kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attr);
> +    if (r) {
> +        error_setg_errno(errp, -r, "KVM_S390_SET_CMMA_BITS failed");
> +    }
> +    return r;
>   }
>
>   static long long kvm_s390_stattrib_get_dirtycount(S390StAttribState *sa)
> diff --git a/hw/s390x/s390-stattrib.c b/hw/s390x/s390-stattrib.c
> index 
> c483b62a9b5f71772639fc180bdad15ecb6711cb..e99de190332a82363b1388bbc450013149295bc0
>  100644
> --- a/hw/s390x/s390-stattrib.c
> +++ b/hw/s390x/s390-stattrib.c
> @@ -60,11 +60,12 @@ void hmp_migrationmode(Monitor *mon, const QDict *qdict)
>       S390StAttribState *sas = s390_get_stattrib_device();
>       S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas);
>       uint64_t what = qdict_get_int(qdict, "mode");
> +    Error *local_err = NULL;
>       int r;
>
> -    r = sac->set_migrationmode(sas, what);
> +    r = sac->set_migrationmode(sas, what, &local_err);
>       if (r < 0) {
> -        monitor_printf(mon, "Error: %s", strerror(-r));
> +        monitor_printf(mon, "Error: %s", error_get_pretty(local_err));

I think we need to free the error here:
error_free(local_err);

Thanks.

>       }
>   }
>
> @@ -170,13 +171,15 @@ static int cmma_save_setup(QEMUFile *f, void *opaque)
>   {
>       S390StAttribState *sas = S390_STATTRIB(opaque);
>       S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas);
> +    Error *local_err = NULL;
>       int res;
>       /*
>        * Signal that we want to start a migration, thus needing PGSTE dirty
>        * tracking.
>        */
> -    res = sac->set_migrationmode(sas, 1);
> +    res = sac->set_migrationmode(sas, true, &local_err);
>       if (res) {
> +        error_report_err(local_err);
>           return res;
>       }
>       qemu_put_be64(f, STATTR_FLAG_EOS);
> @@ -260,7 +263,7 @@ static void cmma_save_cleanup(void *opaque)
>   {
>       S390StAttribState *sas = S390_STATTRIB(opaque);
>       S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas);
> -    sac->set_migrationmode(sas, 0);
> +    sac->set_migrationmode(sas, false, NULL);
>   }
>
>   static bool cmma_active(void *opaque)
> @@ -293,7 +296,8 @@ static long long 
> qemu_s390_get_dirtycount_stub(S390StAttribState *sa)
>   {
>       return 0;
>   }
> -static int qemu_s390_set_migrationmode_stub(S390StAttribState *sa, bool value)
> +static int qemu_s390_set_migrationmode_stub(S390StAttribState *sa, bool value,
> +                                            Error **errp)
>   {
>       return 0;
>   }
> --
> 2.44.0