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

[Greg Kurz]

On Tue, 4 Jun 2019 22:04:21 +0200
Greg Kurz <address@hidden> wrote:

> On Tue, 4 Jun 2019 12:34:37 +0530
> Aravinda Prasad <address@hidden> wrote:
> 
> > On Monday 03 June 2019 09:10 PM, Greg Kurz wrote:  
> > > 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.    
> > 
> > Sure.
> > 
> >   
> > >     
> > >>  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;  
> 
> And also you can drop the parens since == as precedence over ?:
> 

... or even better make it spapr->guest_machine_check_addr != -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
> > >>
> > >>    
> > >     
> >   
> 
>