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

[Michael Roth]

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?

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 */
> -- 
> 2.14.3
>