Re: [Qemu-devel] [Qemu-ppc] [PATCH v9 6/6] migration: Include migration support for machine check handling

[Greg Kurz]

On Wed, 29 May 2019 11:10:57 +0530
Aravinda Prasad <address@hidden> wrote:

> This patch includes migration support for machine check
> handling. Especially this patch blocks VM migration
> requests until the machine check error handling is
> complete as (i) these errors are specific to the source
> hardware and is irrelevant on the target hardware,
> (ii) these errors cause data corruption and should
> be handled before migration.
> 
> Signed-off-by: Aravinda Prasad <address@hidden>
> ---

LGTM, just one issue: machine reset should del and free the blocker as well,
otherwise QEMU would crash if spapr_mce_req_event() is called again.

>  hw/ppc/spapr.c         |   20 ++++++++++++++++++++
>  hw/ppc/spapr_events.c  |   17 +++++++++++++++++
>  hw/ppc/spapr_rtas.c    |    4 ++++
>  include/hw/ppc/spapr.h |    2 ++
>  4 files changed, 43 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e8a77636..31c4850 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2104,6 +2104,25 @@ static const VMStateDescription vmstate_spapr_dtb = {
>      },
>  };
>  
> +static bool spapr_fwnmi_needed(void *opaque)
> +{
> +    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
> +
> +    return (spapr->guest_machine_check_addr == -1) ? 0 : 1;
> +}
> +
> +static const VMStateDescription vmstate_spapr_machine_check = {
> +    .name = "spapr_machine_check",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = spapr_fwnmi_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT64(guest_machine_check_addr, SpaprMachineState),
> +        VMSTATE_INT32(mc_status, SpaprMachineState),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
>  static const VMStateDescription vmstate_spapr = {
>      .name = "spapr",
>      .version_id = 3,
> @@ -2137,6 +2156,7 @@ static const VMStateDescription vmstate_spapr = {
>          &vmstate_spapr_dtb,
>          &vmstate_spapr_cap_large_decr,
>          &vmstate_spapr_cap_ccf_assist,
> +        &vmstate_spapr_machine_check,
>          NULL
>      }
>  };
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index 573c0b7..35e21e4 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -41,6 +41,7 @@
>  #include "qemu/bcd.h"
>  #include "hw/ppc/spapr_ovec.h"
>  #include <libfdt.h>
> +#include "migration/blocker.h"
>  
>  #define RTAS_LOG_VERSION_MASK                   0xff000000
>  #define   RTAS_LOG_VERSION_6                    0x06000000
> @@ -855,6 +856,22 @@ static void spapr_mce_dispatch_elog(PowerPCCPU *cpu, 
> bool recovered)
>  void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
>  {
>      SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> +    int ret;
> +    Error *local_err = NULL;
> +
> +    error_setg(&spapr->fwnmi_migration_blocker,
> +            "Live migration not supported during machine check handling");
> +    ret = migrate_add_blocker(spapr->fwnmi_migration_blocker, &local_err);
> +    if (ret < 0) {
> +        /*
> +         * We don't want to abort and let the migration to continue. In a
> +         * rare case, the machine check handler will run on the target
> +         * hardware. Though this is not preferable, it is better than 
> aborting
> +         * the migration or killing the VM.
> +         */
> +        error_free(spapr->fwnmi_migration_blocker);
> +        warn_report_err(local_err);
> +    }
>  
>      while (spapr->mc_status != -1) {
>          /*
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 91a7ab9..c849223 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -50,6 +50,7 @@
>  #include "target/ppc/mmu-hash64.h"
>  #include "target/ppc/mmu-book3s-v3.h"
>  #include "kvm_ppc.h"
> +#include "migration/blocker.h"
>  
>  static void rtas_display_character(PowerPCCPU *cpu, SpaprMachineState *spapr,
>                                     uint32_t token, uint32_t nargs,
> @@ -404,6 +405,9 @@ static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
>          spapr->mc_status = -1;
>          qemu_cond_signal(&spapr->mc_delivery_cond);
>          rtas_st(rets, 0, RTAS_OUT_SUCCESS);
> +        migrate_del_blocker(spapr->fwnmi_migration_blocker);
> +        error_free(spapr->fwnmi_migration_blocker);
> +        spapr->fwnmi_migration_blocker = NULL;
>      }
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index bd75d4b..6c0cfd8 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -214,6 +214,8 @@ struct SpaprMachineState {
>      SpaprCapabilities def, eff, mig;
>  
>      unsigned gpu_numa_id;
> +
> +    Error *fwnmi_migration_blocker;
>  };
>  
>  #define H_SUCCESS         0
> 
>