On Fri, Nov 04, 2016 at 04:58:47PM +1100, Alexey Kardashevskiy wrote:
> On 30/10/16 22:12, David Gibson wrote:
> > Server-class POWER CPUs can be put into several compatibility modes. These
> > can be specified on the command line, or negotiated by the guest during
> > boot.
> >
> > Currently we don't migrate the compatibility mode, which means after a
> > migration the guest will revert to running with whatever compatibility
> > mode (or none) specified on the command line.
> >
> > With the limited range of CPUs currently used, this doesn't usually cause
> > a problem, but it could. Fix this by adding the compatibility mode (if
> > set) to the migration stream.
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > target-ppc/machine.c | 34 ++++++++++++++++++++++++++++++++++
> > 1 file changed, 34 insertions(+)
> >
> > diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> > index 4820f22..5d87ff6 100644
> > --- a/target-ppc/machine.c
> > +++ b/target-ppc/machine.c
> > @@ -9,6 +9,7 @@
> > #include "mmu-hash64.h"
> > #include "migration/cpu.h"
> > #include "exec/exec-all.h"
> > +#include "qapi/error.h"
> >
> > static int cpu_load_old(QEMUFile *f, void *opaque, int version_id)
> > {
> > @@ -176,6 +177,20 @@ static int cpu_post_load(void *opaque, int version_id)
> > * software has to take care of running QEMU in a compatible mode.
> > */
> > env->spr[SPR_PVR] = env->spr_cb[SPR_PVR].default_value;
> > +
> > +#if defined(TARGET_PPC64)
> > + if (cpu->compat_pvr) {
> > + Error *local_err = NULL;
> > +
> > + ppc_set_compat(cpu, cpu->compat_pvr, &local_err);
> > + if (local_err) {
> > + error_report_err(local_err);
> > + error_free(local_err);
> > + return -1;
> > + }
> > + }
> > +#endif
> > +
> > env->lr = env->spr[SPR_LR];
> > env->ctr = env->spr[SPR_CTR];
> > cpu_write_xer(env, env->spr[SPR_XER]);
> > @@ -528,6 +543,24 @@ static const VMStateDescription vmstate_tlbmas = {
> > }
> > };
> >
> > +static bool compat_needed(void *opaque)
> > +{
> > + PowerPCCPU *cpu = opaque;
> > +
> > + return cpu->compat_pvr != 0;
>
>
> Finally got to trying how this affects migration :)
>
> This breaks migration to QEMU <=2.7, and it should not at least when both
> source and destination are running with -cpu host,compat=power7.
IIUC, we don't generally try to maintain backwards migration, even for
old machine types.
>
>
> > +}
> > +
> > +static const VMStateDescription vmstate_compat = {
> > + .name = "cpu/compat",
> > + .version_id = 1,
> > + .minimum_version_id = 1,
> > + .needed = compat_needed,
> > + .fields = (VMStateField[]) {
> > + VMSTATE_UINT32(compat_pvr, PowerPCCPU),
> > + VMSTATE_END_OF_LIST()
> > + }
> > +};
> > +
> > const VMStateDescription vmstate_ppc_cpu = {
> > .name = "cpu",
> > .version_id = 5,
> > @@ -580,6 +613,7 @@ const VMStateDescription vmstate_ppc_cpu = {
> > &vmstate_tlb6xx,
> > &vmstate_tlbemb,
> > &vmstate_tlbmas,
> > + &vmstate_compat,
> > NULL
> > }
> > };
> >
>
>
--
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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