Re: [Qemu-ppc] [RFC for-2.12 4/8] spapr: Validate capabilities on migration

[David Gibson]

On Mon, Dec 11, 2017 at 06:05:39PM -0600, Michael Roth wrote:
> Quoting David Gibson (2017-12-11 01:08:04)
> > Now that the "pseries" machine type implements optional capabilities (well,
> > one so far) there's the possibility of having different capabilities
> > available at either end of a migration.  Although arguably a user error,
> > it would be nice to catch this situation and fail as gracefully as we can.
> > 
> > This adds code to migrate the capabilities flags.  These aren't pulled
> > directly into the destination's configuration since what the user has
> > specified on the destination command line should take precedence.  However,
> > they are checked against the destination capabilities.
> > 
> > If the source was using a capability which is absent on the destination,
> > we fail the migration, since that could easily cause a guest crash or other
> > bad behaviour.  If the source lacked a capability which is present on the
> > destination we warn, but allow the migration to proceed.
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  hw/ppc/spapr.c         |  6 ++++
> >  hw/ppc/spapr_caps.c    | 94 
> > ++++++++++++++++++++++++++++++++++++++++++++++++--
> >  include/hw/ppc/spapr.h |  6 ++++
> >  3 files changed, 103 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 0487d67894..4e4cf35587 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1587,6 +1587,11 @@ static int spapr_post_load(void *opaque, int 
> > version_id)
> >      sPAPRMachineState *spapr = (sPAPRMachineState *)opaque;
> >      int err = 0;
> > 
> > +    err = spapr_caps_post_migration(spapr);
> > +    if (err) {
> > +        return err;
> > +    }
> > +
> >      if (!object_dynamic_cast(OBJECT(spapr->ics), TYPE_ICS_KVM)) {
> >          CPUState *cs;
> >          CPU_FOREACH(cs) {
> > @@ -1753,6 +1758,7 @@ static const VMStateDescription vmstate_spapr = {
> >          &vmstate_spapr_ov5_cas,
> >          &vmstate_spapr_patb_entry,
> >          &vmstate_spapr_pending_events,
> > +        &vmstate_spapr_caps,
> >          NULL
> >      }
> >  };
> > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > index 5afb4d9d5f..6bba04d60e 100644
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -22,6 +22,7 @@
> >   * THE SOFTWARE.
> >   */
> >  #include "qemu/osdep.h"
> > +#include "qemu/error-report.h"
> >  #include "qapi/error.h"
> >  #include "qapi/visitor.h"
> >  #include "sysemu/hw_accel.h"
> > @@ -61,6 +62,91 @@ static sPAPRCapabilities 
> > default_caps_with_cpu(sPAPRMachineState *spapr, CPUStat
> >      return caps;
> >  }
> > 
> > +static bool spapr_caps_needed(void *opaque)
> > +{
> > +    sPAPRMachineState *spapr = opaque;
> > +
> > +    return (spapr->forced_caps.mask != 0) || (spapr->forbidden_caps.mask 
> > != 0);
> > +}
> > +
> > +/* This has to be called from the top-level spapr post_load, not the
> > + * caps specific one.  Otherwise it wouldn't be called when the source
> > + * caps are all defaults, which could still conflict with overridden
> > + * caps on the destination */
> > +int spapr_caps_post_migration(sPAPRMachineState *spapr)
> > +{
> > +    uint64_t allcaps = 0;
> > +    int i;
> > +    bool ok = true;
> > +    sPAPRCapabilities dstcaps = spapr->effective_caps;
> > +    sPAPRCapabilities srccaps;
> > +
> > +    srccaps = default_caps_with_cpu(spapr, first_cpu);
> > +    srccaps.mask |= spapr->mig_forced_caps.mask;
> > +    srccaps.mask &= ~spapr->mig_forbidden_caps.mask;
> > +
> > +    for (i = 0; i < ARRAY_SIZE(capability_table); i++) {
> > +        sPAPRCapabilityInfo *info = &capability_table[i];
> > +
> > +        allcaps |= info->bit;
> > +
> > +        if ((srccaps.mask & info->bit) && !(dstcaps.mask & info->bit)) {
> > +            error_report("cap-%s=on in incoming stream, but off in 
> > destination",
> > +                         info->name);
> > +            ok = false;
> > +        }
> > +
> > +        if (!(srccaps.mask & info->bit) && (dstcaps.mask & info->bit)) {
> > +            error_report("Warning: cap-%s=off in incoming stream, but on 
> > in destination",
> > +                         info->name);
> > +        }
> > +    }
> > +
> > +    if (spapr->mig_forced_caps.mask & ~allcaps) {
> > +        error_report("Unknown capabilities 0x%"PRIx64" enabled in incoming 
> > stream",
> > +                     spapr->forced_caps.mask & ~allcaps);
> 
> Shouldn't these be spapr->mig_forced_caps.mask,
> 
> > +        ok = false;
> > +    }
> > +    if (spapr->mig_forbidden_caps.mask & ~allcaps) {
> > +        error_report("Warning: Unknown capabilities 0x%"PRIx64" disabled 
> > in incoming stream",
> > +                     spapr->forbidden_caps.mask & ~allcaps);
> 
> and spapr->mig_forbidden_caps.mask?

Yes, they should.  Nice catch.

> 
> Looks good otherwise.
> 
> > +    }
> > +
> > +    return ok ? 0 : -EINVAL;
> > +}
> > +
> > +static int spapr_caps_pre_save(void *opaque)
> > +{
> > +    sPAPRMachineState *spapr = opaque;
> > +
> > +    spapr->mig_forced_caps = spapr->forced_caps;
> > +    spapr->mig_forbidden_caps = spapr->forbidden_caps;
> > +    return 0;
> > +}
> > +
> > +static int spapr_caps_pre_load(void *opaque)
> > +{
> > +    sPAPRMachineState *spapr = opaque;
> > +
> > +    spapr->mig_forced_caps = spapr_caps(0);
> > +    spapr->mig_forbidden_caps = spapr_caps(0);
> > +    return 0;
> > +}
> > +
> > +const VMStateDescription vmstate_spapr_caps = {
> > +    .name = "spapr/caps",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .needed = spapr_caps_needed,
> > +    .pre_save = spapr_caps_pre_save,
> > +    .pre_load = spapr_caps_pre_load,
> > +    .fields = (VMStateField[]) {
> > +        VMSTATE_UINT64(mig_forced_caps.mask, sPAPRMachineState),
> > +        VMSTATE_UINT64(mig_forbidden_caps.mask, sPAPRMachineState),
> > +        VMSTATE_END_OF_LIST()
> > +    },
> > +};
> > +
> >  static void spapr_allow_caps(sPAPRMachineState *spapr, Error **errp)
> >  {
> >      Error *err = NULL;
> > @@ -98,6 +184,11 @@ void spapr_caps_reset(sPAPRMachineState *spapr)
> > 
> >      caps = default_caps_with_cpu(spapr, first_cpu);
> > 
> > +    /* Remove unnecessary forced/forbidden bits (this will help us
> > +     * with migration) */
> > +    spapr->forced_caps.mask &= ~caps.mask;
> > +    spapr->forbidden_caps.mask &= caps.mask;
> > +
> >      caps.mask |= spapr->forced_caps.mask;
> >      caps.mask &= ~spapr->forbidden_caps.mask;
> > 
> > @@ -168,9 +259,6 @@ void spapr_validate_caps(sPAPRMachineState *spapr, 
> > Error **errp)
> >          error_setg(&local_err, "Some sPAPR capabilities set both on and 
> > off");
> >          return;
> >      }
> > -
> > -    /* Check for any caps incompatible with other caps.  Nothing to do
> > -     * yet */
> >  }
> > 
> >  void spapr_capability_properties(sPAPRMachineClass *smc, Error **errp)
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index 4215b113f4..9b80fe72ed 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -54,6 +54,8 @@ typedef enum {
> >   * Capabilities
> >   */
> > 
> > +/* These bits go in the migration stream, so they can't be reassigned */
> > +
> >  /* Hardware Transactional Memory */
> >  #define SPAPR_CAP_HTM               0x0000000000000001ULL
> > 
> > @@ -142,6 +144,7 @@ struct sPAPRMachineState {
> >      const char *icp_type;
> > 
> >      sPAPRCapabilities forced_caps, forbidden_caps;
> > +    sPAPRCapabilities mig_forced_caps, mig_forbidden_caps;
> >      sPAPRCapabilities effective_caps;
> >  };
> > 
> > @@ -743,6 +746,8 @@ qemu_irq spapr_qirq(sPAPRMachineState *spapr, int irq);
> >  /*
> >   * Handling of optional capabilities
> >   */
> > +extern const VMStateDescription vmstate_spapr_caps;
> > +
> >  static inline sPAPRCapabilities spapr_caps(uint64_t mask)
> >  {
> >      sPAPRCapabilities caps = { mask };
> > @@ -757,5 +762,6 @@ static inline bool spapr_has_cap(sPAPRMachineState 
> > *spapr, uint64_t cap)
> >  void spapr_caps_reset(sPAPRMachineState *spapr);
> >  void spapr_validate_caps(sPAPRMachineState *spapr, Error **errp);
> >  void spapr_capability_properties(sPAPRMachineClass *smc, Error **errp);
> > +int spapr_caps_post_migration(sPAPRMachineState *spapr);
> > 
> >  #endif /* HW_SPAPR_H */
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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