On Thu, 6 Jun 2019 13:06:14 +1000 David Gibson <da...@gibson.dropbear.id.au> wrote:
> On Wed, May 29, 2019 at 11:10:57AM +0530, Aravinda Prasad 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 <aravi...@linux.vnet.ibm.com>
> > ---
> > 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;
>
> Since we're introducing a PAPR capability to enable this, it would
> actually be better to check that here, rather than the runtime state.
> That leads to less cases and easier to understand semantics for the
> migration stream.
>
Hmmm... the purpose of needed() VMState callbacks is precisely about
runtime state: the subsection should only be migrated if an MCE is
pending, ie. 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);
>
> You should set fwnmi_migration_blocker to NULL here as well.
>
> As mentioned on an earlier iteration, the migration blocker is the
> same every time. Couldn't you just create it once and free at final
> teardown, rather than recreating it for every NMI?
>
> > + 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
> >
>
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