On 21/11/16 16:31, David Gibson wrote:
> Until very recently, the vmstate for ppc cpus included some poorly
> thought out VMSTATE_EQUAL() components, that can easily break
> migration compatibility, and did so between qemu-2.6 and later
> versions. A hack was recently added which fixes this migration
> breakage, but it leaves the unhelpful cruft of these fields in the
> migration stream.
>
> dThis patch adds a new cpu property allowing these fields to be
> removed from the stream entirely. This property is enabled by default
> for the pseries-2.8 machine type - which comes after the fix - and for
> all non-pseries machine types - which aren't mature enough to care
> about cross-version migration.
>
> The migration hack remains in place for pseries-2.7 and earlier
> machine types, allowing backwards and forwards migration with the
> older machine types.
>
> This restricts the migration compatibility cruft to older machine
> types, and at least opens the possibility of eventually deprecating
> and removing it entirely.
>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
> hw/ppc/spapr.c | 5 +++++
> target-ppc/cpu.h | 3 ++-
> target-ppc/machine.c | 26 ++++++++++++++++++--------
> target-ppc/translate_init.c | 6 ++++++
> 4 files changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 54b88d3..775ad2e 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2767,6 +2767,11 @@ DEFINE_SPAPR_MACHINE(2_8, "2.8", true);
> .driver = TYPE_SPAPR_PCI_HOST_BRIDGE, \
> .property = "mem64_win_size", \
> .value = "0", \
> + }, \
> + { \
> + .driver = TYPE_POWERPC_CPU, \
> + .property = "pre-2.8-migration", \
> + .value = "on", \
> },
>
> static void phb_placement_2_7(sPAPRMachineState *spapr, uint32_t index,
> diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
> index 7798b2e..2a50c43 100644
> --- a/target-ppc/cpu.h
> +++ b/target-ppc/cpu.h
> @@ -1167,7 +1167,8 @@ struct PowerPCCPU {
> uint32_t max_compat;
> uint32_t cpu_version;
>
> - /* fields used only during migration for compatibility hacks */
> + /* Fields related to migration compatibility hacks */
> + bool pre_2_8_migration;
> target_ulong mig_msr_mask;
> uint64_t mig_insns_flags;
> uint64_t mig_insns_flags2;
> diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> index fcac263..18c16d2 100644
> --- a/target-ppc/machine.c
> +++ b/target-ppc/machine.c
> @@ -135,6 +135,13 @@ static const VMStateInfo vmstate_info_avr = {
> #define VMSTATE_AVR_ARRAY(_f, _s, _n) \
> VMSTATE_AVR_ARRAY_V(_f, _s, _n, 0)
>
> +static bool cpu_pre_2_8_migration(void *opaque, int version_id)
> +{
> + PowerPCCPU *cpu = opaque;
> +
> + return cpu->pre_2_8_migration;
> +}
> +
> static void cpu_pre_save(void *opaque)
> {
> PowerPCCPU *cpu = opaque;
> @@ -178,10 +185,12 @@ static void cpu_pre_save(void *opaque)
> }
>
> /* Hacks for migration compatibility between 2.6, 2.7 & 2.8 */
> - cpu->mig_msr_mask = env->msr_mask;
> - cpu->mig_insns_flags = env->insns_flags & insns_compat_mask;
> - cpu->mig_insns_flags2 = env->insns_flags2 & insns_compat_mask2;
> - cpu->mig_nb_BATs = env->nb_BATs;
> + if (cpu->pre_2_8_migration) {
> + cpu->mig_msr_mask = env->msr_mask;
> + cpu->mig_insns_flags = env->insns_flags & insns_compat_mask;
> + cpu->mig_insns_flags2 = env->insns_flags2 & insns_compat_mask2;
> + cpu->mig_nb_BATs = env->nb_BATs;
> + }
> }
>
> static int cpu_post_load(void *opaque, int version_id)
> @@ -582,10 +591,11 @@ const VMStateDescription vmstate_ppc_cpu = {
> /* FIXME: access_type? */
>
> /* Sanity checking */
> - VMSTATE_UINTTL(mig_msr_mask, PowerPCCPU),
> - VMSTATE_UINT64(mig_insns_flags, PowerPCCPU),
> - VMSTATE_UINT64(mig_insns_flags2, PowerPCCPU),
> - VMSTATE_UINT32(mig_nb_BATs, PowerPCCPU),
> + VMSTATE_UINTTL_TEST(mig_msr_mask, PowerPCCPU, cpu_pre_2_8_migration),
> + VMSTATE_UINT64_TEST(mig_insns_flags, PowerPCCPU,
> cpu_pre_2_8_migration),
> + VMSTATE_UINT64_TEST(mig_insns_flags2, PowerPCCPU,
> + cpu_pre_2_8_migration),
> + VMSTATE_UINT32_TEST(mig_nb_BATs, PowerPCCPU, cpu_pre_2_8_migration),
> VMSTATE_END_OF_LIST()
> },
> .subsections = (const VMStateDescription*[]) {
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index 208fa1e..626e031 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -10520,6 +10520,11 @@ static gchar *ppc_gdb_arch_name(CPUState *cs)
> #endif
> }
>
> +static Property ppc_cpu_properties[] = {
> + DEFINE_PROP_BOOL("pre-2.8-migration", PowerPCCPU, pre_2_8_migration,
> false),
> + DEFINE_PROP_END_OF_LIST(),
> +};
> +
> static void ppc_cpu_class_init(ObjectClass *oc, void *data)
> {
> PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
> @@ -10532,6 +10537,7 @@ static void ppc_cpu_class_init(ObjectClass *oc, void
> *data)
> pcc->interrupts_big_endian = ppc_cpu_interrupts_big_endian_always;
> dc->realize = ppc_cpu_realizefn;
> dc->unrealize = ppc_cpu_unrealizefn;
> + dc->props = ppc_cpu_properties;
>
> pcc->parent_reset = cc->reset;
> cc->reset = ppc_cpu_reset;
>
--
Alexey
