Re: [PATCH v20 6/7] migration: Include migration support for machine check handling

[Ganesh <ganeshgr@linux.ibm.com>]

On 1/20/20 6:18 AM, David Gibson wrote:
> On Fri, Jan 17, 2020 at 03:08:54PM +0530, Ganesh Goudar wrote:
>> From: Aravinda Prasad <arawinda.p@gmail.com>
>>
>> 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 these errors are specific to the source
>> hardware and is irrelevant on the target hardware.
>>
>> Signed-off-by: Aravinda Prasad <arawinda.p@gmail.com>
>> [Do not set FWNMI cap in post_load, now its done in .apply hook]
>> Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
>> ---
>>   hw/ppc/spapr.c         | 47 ++++++++++++++++++++++++++++++++++++++++++
>>   hw/ppc/spapr_events.c  | 16 +++++++++++++-
>>   hw/ppc/spapr_rtas.c    |  2 ++
>>   include/hw/ppc/spapr.h |  2 ++
>>   4 files changed, 66 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index 46bac1a83c..c8bc2fa9f3 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -46,6 +46,7 @@
>>   #include "migration/qemu-file-types.h"
>>   #include "migration/global_state.h"
>>   #include "migration/register.h"
>> +#include "migration/blocker.h"
>>   #include "mmu-hash64.h"
>>   #include "mmu-book3s-v3.h"
>>   #include "cpu-models.h"
>> @@ -1683,6 +1684,8 @@ static void spapr_machine_reset(MachineState *machine)
>>   
>>       /* Signal all vCPUs waiting on this condition */
>>       qemu_cond_broadcast(&spapr->mc_delivery_cond);
>> +
>> +    migrate_del_blocker(spapr->fwnmi_migration_blocker);
> Thinking on our discussions about this earlier, there are
> circumstances where we could add the blocker message multiple times.
> IIUC, this will just remove one of them, but at reset, we need to
> remove all of them.
Sorry I did not mention it in our previous conversation, here machine 
check events
are serialized, Aravinda has explained it clear in commit message of 
patch 5/7, So
there will be a single entry in the list.
>
>>   }
>>   
>>   static void spapr_create_nvram(SpaprMachineState *spapr)
>> @@ -1965,6 +1968,42 @@ static const VMStateDescription vmstate_spapr_dtb = {
>>       },
>>   };
>>   
>> +static bool spapr_fwnmi_needed(void *opaque)
>> +{
>> +    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
>> +
>> +    return spapr->guest_machine_check_addr != -1;
>> +}
>> +
>> +static int spapr_fwnmi_pre_save(void *opaque)
>> +{
>> +    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
>> +
>> +    /*
>> +     * Check if machine check handling is in progress and print a
>> +     * warning message.
>> +     */
>> +    if (spapr->mc_status != -1) {
>> +        warn_report("A machine check is being handled during migration. The"
>> +                "handler may run and log hardware error on the destination");
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static const VMStateDescription vmstate_spapr_machine_check = {
>> +    .name = "spapr_machine_check",
>> +    .version_id = 1,
>> +    .minimum_version_id = 1,
>> +    .needed = spapr_fwnmi_needed,
>> +    .pre_save = spapr_fwnmi_pre_save,
>> +    .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,
>> @@ -1999,6 +2038,7 @@ static const VMStateDescription vmstate_spapr = {
>>           &vmstate_spapr_cap_large_decr,
>>           &vmstate_spapr_cap_ccf_assist,
>>           &vmstate_spapr_cap_fwnmi,
>> +        &vmstate_spapr_machine_check,
>>           NULL
>>       }
>>   };
>> @@ -2814,6 +2854,13 @@ static void spapr_machine_init(MachineState *machine)
>>           spapr_create_lmb_dr_connectors(spapr);
>>       }
>>   
>> +    if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI_MCE) == SPAPR_CAP_ON) {
>> +        /* Create the error string for live migration blocker */
>> +        error_setg(&spapr->fwnmi_migration_blocker,
>> +            "A machine check is being handled during migration. The handler"
>> +            "may run and log hardware error on the destination");
>> +    }
>> +
>>       /* Set up RTAS event infrastructure */
>>       spapr_events_init(spapr);
>>   
>> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
>> index 54eaf28a9e..884e455f02 100644
>> --- a/hw/ppc/spapr_events.c
>> +++ b/hw/ppc/spapr_events.c
>> @@ -43,6 +43,7 @@
>>   #include "qemu/main-loop.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
>> @@ -843,6 +844,8 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
>>   {
>>       SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>>       CPUState *cs = CPU(cpu);
>> +    int ret;
>> +    Error *local_err = NULL;
>>   
>>       if (spapr->guest_machine_check_addr == -1) {
>>           /*
>> @@ -872,8 +875,19 @@ void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
>>               return;
>>           }
>>       }
>> -    spapr->mc_status = cpu->vcpu_id;
>>   
>> +    ret = migrate_add_blocker(spapr->fwnmi_migration_blocker, &local_err);
>> +    if (ret == -EBUSY) {
>> +        /*
>> +         * We don't want to abort so we let the migration to continue.
>> +         * In a rare case, the machine check handler will run on the target.
>> +         * Though this is not preferable, it is better than aborting
>> +         * the migration or killing the VM.
>> +         */
>> +        warn_report("Received a fwnmi while migration was in progress");
>> +    }
>> +
>> +    spapr->mc_status = cpu->vcpu_id;
>>       spapr_mce_dispatch_elog(cpu, recovered);
>>   }
>>   
>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>> index 3f162d82f5..4ce8e48d2a 100644
>> --- a/hw/ppc/spapr_rtas.c
>> +++ b/hw/ppc/spapr_rtas.c
>> @@ -50,6 +50,7 @@
>>   #include "hw/ppc/fdt.h"
>>   #include "target/ppc/mmu-hash64.h"
>>   #include "target/ppc/mmu-book3s-v3.h"
>> +#include "migration/blocker.h"
>>   
>>   static void rtas_display_character(PowerPCCPU *cpu, SpaprMachineState *spapr,
>>                                      uint32_t token, uint32_t nargs,
>> @@ -453,6 +454,7 @@ 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);
>>   }
>>   
>>   static struct rtas_call {
>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>> index f6f82d88aa..a1fba95c82 100644
>> --- a/include/hw/ppc/spapr.h
>> +++ b/include/hw/ppc/spapr.h
>> @@ -218,6 +218,8 @@ struct SpaprMachineState {
>>   
>>       unsigned gpu_numa_id;
>>       SpaprTpmProxy *tpm_proxy;
>> +
>> +    Error *fwnmi_migration_blocker;
>>   };
>>   
>>   #define H_SUCCESS         0