On Fri, 20 Oct 2023 17:49:38 +1000 "Nicholas Piggin" <npig...@gmail.com> wrote:
> On Fri Oct 20, 2023 at 7:39 AM AEST, Greg Kurz wrote: > > On Thu, 19 Oct 2023 21:08:25 +0200 > > Juan Quintela <quint...@redhat.com> wrote: > > > > > Current code does: > > > - register pre_2_10_vmstate_dummy_icp with "icp/server" and instance > > > dependinfg on cpu number > > > - for newer machines, it register vmstate_icp with "icp/server" name > > > and instance 0 > > > - now it unregisters "icp/server" for the 1st instance. > > > > > > This is wrong at many levels: > > > - we shouldn't have two VMSTATEDescriptions with the same name > > > - In case this is the only solution that we can came with, it needs to > > > be: > > > * register pre_2_10_vmstate_dummy_icp > > > * unregister pre_2_10_vmstate_dummy_icp > > > * register real vmstate_icp > > > > > > As the initialization of this machine is already complex enough, I > > > need help from PPC maintainers to fix this. > > > > > > Volunteers? > > > > > > CC: Cedric Le Goater <c...@kaod.org> > > > CC: Daniel Henrique Barboza <danielhb...@gmail.com> > > > CC: David Gibson <da...@gibson.dropbear.id.au> > > > CC: Greg Kurz <gr...@kaod.org> > > > > > > Signed-off-by: Juan Quintela <quint...@redhat.com> > > > --- > > > hw/ppc/spapr.c | 7 ++++++- > > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > > index cb840676d3..8531d13492 100644 > > > --- a/hw/ppc/spapr.c > > > +++ b/hw/ppc/spapr.c > > > @@ -143,7 +143,12 @@ static bool pre_2_10_vmstate_dummy_icp_needed(void > > > *opaque) > > > } > > > > > > static const VMStateDescription pre_2_10_vmstate_dummy_icp = { > > > - .name = "icp/server", > > > + /* > > > + * Hack ahead. We can't have two devices with the same name and > > > + * instance id. So I rename this to pass make check. > > > + * Real help from people who knows the hardware is needed. > > > + */ > > > + .name = "pre-2.10-icp/server", > > > .version_id = 1, > > > .minimum_version_id = 1, > > > .needed = pre_2_10_vmstate_dummy_icp_needed, > > > > I guess this fix is acceptable as well and a lot simpler than > > reverting the hack actually. Outcome is the same : drop > > compat with pseries-2.9 and older. > > > > Reviewed-by: Greg Kurz <gr...@kaod.org> > > So the reason we can't have duplicate names registered, aside from it > surely going bad if we actually send or receive a stream at the point > they are registered, is the duplcate check introduced in patch 9? But > before that, this hack does seem to actually work because the duplicate > is unregistered right away. > Correct. > If I understand the workaround, there is an asymmetry in the migration > sequence in that receiving an unexpected object would cause a failure, > but going from newer to older would just skip some "expected" objects > and that didn't cause a problem. So you only have to deal with ignoring > the unexpected ones going form older to newer. > Correct. > Side question, is it possible to flag the problem of *not* receiving > an object that you did expect? That might be a source of bugs too. > AFAICR we try to only migrate state that differs from reset : the destination cannot really assume it will receive anything for a given device. > Anyway, I wonder if we could fix this spapr problem by adding a special > case wild card instance matcher to ignore it? It's still a bit hacky > but maybe a bit nicer. I don't mind deprecating the machine soon if > you want to clear the wildcard hack away soon, but it would be nice to > separate the deprecation and removal from the fix, if possible. > > This patch is not tested but hopefully helps illustrate the idea. > I'm not sure this will fly with older QEMUs that don't know about VMSTATE_INSTANCE_ID_WILD... but I'll let Juan comment on that. > Thanks, > Nick > Cheers, -- Greg > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > index 1a31fb7293..8ce03edefa 100644 > --- a/include/migration/vmstate.h > +++ b/include/migration/vmstate.h > @@ -1205,6 +1205,7 @@ int vmstate_save_state_v(QEMUFile *f, const > VMStateDescription *vmsd, > bool vmstate_save_needed(const VMStateDescription *vmsd, void *opaque); > > #define VMSTATE_INSTANCE_ID_ANY -1 > +#define VMSTATE_INSTANCE_ID_WILD -2 > > /* Returns: 0 on success, -1 on failure */ > int vmstate_register_with_alias_id(VMStateIf *obj, uint32_t instance_id, > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index cb840676d3..2418899dd4 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -155,16 +155,10 @@ static const VMStateDescription > pre_2_10_vmstate_dummy_icp = { > }, > }; > > -static void pre_2_10_vmstate_register_dummy_icp(int i) > +static void pre_2_10_vmstate_register_dummy_icp(void) > { > - vmstate_register(NULL, i, &pre_2_10_vmstate_dummy_icp, > - (void *)(uintptr_t) i); > -} > - > -static void pre_2_10_vmstate_unregister_dummy_icp(int i) > -{ > - vmstate_unregister(NULL, &pre_2_10_vmstate_dummy_icp, > - (void *)(uintptr_t) i); > + vmstate_register(NULL, VMSTATE_INSTANCE_ID_WILD, > + &pre_2_10_vmstate_dummy_icp, NULL); > } > > int spapr_max_server_number(SpaprMachineState *spapr) > @@ -2665,12 +2659,10 @@ static void spapr_init_cpus(SpaprMachineState *spapr) > } > > if (smc->pre_2_10_has_unused_icps) { > - for (i = 0; i < spapr_max_server_number(spapr); i++) { > - /* Dummy entries get deregistered when real ICPState objects > - * are registered during CPU core hotplug. > - */ > - pre_2_10_vmstate_register_dummy_icp(i); > - } > + /* Dummy entries get deregistered when real ICPState objects > + * are registered during CPU core hotplug. > + */ > + pre_2_10_vmstate_register_dummy_icp(); > } > > for (i = 0; i < possible_cpus->len; i++) { > @@ -3873,21 +3865,9 @@ void spapr_core_release(DeviceState *dev) > static void spapr_core_unplug(HotplugHandler *hotplug_dev, DeviceState *dev) > { > MachineState *ms = MACHINE(hotplug_dev); > - SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(ms); > CPUCore *cc = CPU_CORE(dev); > CPUArchId *core_slot = spapr_find_cpu_slot(ms, cc->core_id, NULL); > > - if (smc->pre_2_10_has_unused_icps) { > - SpaprCpuCore *sc = SPAPR_CPU_CORE(OBJECT(dev)); > - int i; > - > - for (i = 0; i < cc->nr_threads; i++) { > - CPUState *cs = CPU(sc->threads[i]); > - > - pre_2_10_vmstate_register_dummy_icp(cs->cpu_index); > - } > - } > - > assert(core_slot); > core_slot->cpu = NULL; > qdev_unrealize(dev); > @@ -3968,10 +3948,8 @@ static void spapr_core_plug(HotplugHandler > *hotplug_dev, DeviceState *dev) > { > SpaprMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev)); > MachineClass *mc = MACHINE_GET_CLASS(spapr); > - SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > SpaprCpuCore *core = SPAPR_CPU_CORE(OBJECT(dev)); > CPUCore *cc = CPU_CORE(dev); > - CPUState *cs; > SpaprDrc *drc; > CPUArchId *core_slot; > int index; > @@ -4018,13 +3996,6 @@ static void spapr_core_plug(HotplugHandler > *hotplug_dev, DeviceState *dev) > &error_abort); > } > } > - > - if (smc->pre_2_10_has_unused_icps) { > - for (i = 0; i < cc->nr_threads; i++) { > - cs = CPU(core->threads[i]); > - pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index); > - } > - } > } > > static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState > *dev, > diff --git a/migration/savevm.c b/migration/savevm.c > index 497ce02bd7..f33449e208 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -989,6 +989,10 @@ static int vmstate_save(QEMUFile *f, SaveStateEntry *se, > JSONWriter *vmdesc) > trace_savevm_section_skip(se->idstr, se->section_id); > return 0; > } > + if (se->instance_id == VMSTATE_INSTANCE_ID_WILD) { > + warn_report("Wildcard vmstate entry must set needed=false"); > + return 0; > + } > > trace_savevm_section_start(se->idstr, se->section_id); > save_section_header(f, se, QEMU_VM_SECTION_FULL); > @@ -1731,13 +1735,16 @@ int qemu_save_device_state(QEMUFile *f) > > static SaveStateEntry *find_se(const char *idstr, uint32_t instance_id) > { > + SaveStateEntry *se_wild = NULL; > SaveStateEntry *se; > > QTAILQ_FOREACH(se, &savevm_state.handlers, entry) { > - if (!strcmp(se->idstr, idstr) && > - (instance_id == se->instance_id || > - instance_id == se->alias_id)) > - return se; > + if (!strcmp(se->idstr, idstr)) { > + if (instance_id == se->instance_id || instance_id == > se->alias_id) > + return se; > + if (se->instance_id == VMSTATE_INSTANCE_ID_WILD) > + se_wild = se; > + } > /* Migrating from an older version? */ > if (strstr(se->idstr, idstr) && se->compat) { > if (!strcmp(se->compat->idstr, idstr) && > @@ -1746,7 +1753,7 @@ static SaveStateEntry *find_se(const char *idstr, > uint32_t instance_id) > return se; > } > } > - return NULL; > + return se_wild; > } > > enum LoadVMExitCodes { -- Greg