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spapr: Don't migrate the hpt_maxpagesize cap to older machine types

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Commit 0b8c89be7f7b added the hpt_maxpagesize capability to the migration
stream. This is okay for new machine types but it breaks backward migration
to older QEMUs, which don't expect the extra subsection.

Add a compatibility boolean flag to the sPAPR machine class and use it to
skip migration of the capability for machine types 4.0 and older. This
fixes migration to an older QEMU. Note that the destination will emit a
warning:

qemu-system-ppc64: warning: cap-hpt-max-page-size lower level (16) in incoming stream than on destination (24)

This is expected and harmless though. It is okay to migrate from a lower
HPT maximum page size (64k) to a greater one (16M).

Fixes: 0b8c89be7f7b "spapr: Add forgotten capability to migration stream"
Based-on: <20190522074016.10521-3-clg@kaod.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <155853262675.1158324.17301777846476373459.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Greg Kurz 2019-05-22 15:43:46 +02:00 • committed by David Gibson
parent bd94bc0647
commit 3725ef1a94
3 changed files with 13 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

1
hw/ppc/spapr.c
View file

@ -4431,6 +4431,7 @@ static void spapr_machine_4_0_class_options(MachineClass *mc)
compat_props_add(mc->compat_props, hw_compat_4_0, hw_compat_4_0_len);
smc->phb_placement = phb_placement_4_0;
smc->irq = &spapr_irq_xics;
smc->pre_4_1_migration = true;
}
DEFINE_SPAPR_MACHINE(4_0, "4.0", false);

12
hw/ppc/spapr_caps.c
View file

@ -64,6 +64,7 @@ typedef struct SpaprCapabilityInfo {
void (*apply)(SpaprMachineState *spapr, uint8_t val, Error **errp);
void (*cpu_apply)(SpaprMachineState *spapr, PowerPCCPU *cpu,
uint8_t val, Error **errp);
bool (*migrate_needed)(void *opaque);
} SpaprCapabilityInfo;
static void spapr_cap_get_bool(Object *obj, Visitor *v, const char *name,
@ -350,6 +351,11 @@ static void cap_hpt_maxpagesize_apply(SpaprMachineState *spapr,
spapr_check_pagesize(spapr, qemu_minrampagesize(), errp);
}
static bool cap_hpt_maxpagesize_migrate_needed(void *opaque)
{
return !SPAPR_MACHINE_GET_CLASS(opaque)->pre_4_1_migration;
}
static bool spapr_pagesize_cb(void *opaque, uint32_t seg_pshift,
uint32_t pshift)
{
@ -542,6 +548,7 @@ SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
.type = "int",
.apply = cap_hpt_maxpagesize_apply,
.cpu_apply = cap_hpt_maxpagesize_cpu_apply,
.migrate_needed = cap_hpt_maxpagesize_migrate_needed,
},
[SPAPR_CAP_NESTED_KVM_HV] = {
.name = "nested-hv",
@ -679,8 +686,11 @@ int spapr_caps_post_migration(SpaprMachineState *spapr)
static bool spapr_cap_##sname##_needed(void *opaque) \
{ \
SpaprMachineState *spapr = opaque; \
bool (*needed)(void *opaque) = \
capability_table[cap].migrate_needed; \
\
return spapr->cmd_line_caps[cap] && \
return needed ? needed(opaque) : true && \
spapr->cmd_line_caps[cap] && \
(spapr->eff.caps[cap] != \
spapr->def.caps[cap]); \
} \