* [PATCH v2 03/16] migration: make .post_save() a void function [not found] <20260220210214.800050-1-vsementsov@yandex-team.ru> @ 2026-02-20 21:02 ` Vladimir Sementsov-Ogievskiy 2026-02-27 22:41 ` Fabiano Rosas 0 siblings, 1 reply; 4+ messages in thread From: Vladimir Sementsov-Ogievskiy @ 2026-02-20 21:02 UTC (permalink / raw) To: peterx Cc: farosas, vsementsov, Pierrick Bouvier, Nicholas Piggin, Harsh Prateek Bora, Peter Maydell, open list:All patches CC here, open list:sPAPR (pseries), open list:ARM TCG CPUs All other handlers now have _errp() variants. Should we go this way for .post_save()? Actually it's rather strange, when the vmstate do successful preparations in .pre_save(), then successfully save all sections and subsections, end then fail when all the state is successfully transferred to the target. Happily, we have only three .post_save() realizations, all always successful. Let's make this a rule. Also note, that we call .post_save() in two places, and handle its (theoretical) failure inconsistently. Fix that too. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> --- docs/devel/migration/main.rst | 2 +- hw/ppc/spapr_pci.c | 3 +-- include/migration/vmstate.h | 10 +++++++++- migration/savevm.c | 3 +-- migration/vmstate.c | 12 +++--------- target/arm/machine.c | 4 +--- 6 files changed, 16 insertions(+), 18 deletions(-) diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst index 234d280249..2de7050764 100644 --- a/docs/devel/migration/main.rst +++ b/docs/devel/migration/main.rst @@ -439,7 +439,7 @@ The functions to do that are inside a vmstate definition, and are called: This function is called before we save the state of one device. -- ``int (*post_save)(void *opaque);`` +- ``void (*post_save)(void *opaque);`` This function is called after we save the state of one device (even upon failure, unless the call to pre_save returned an error). diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c index ea998bdff1..1dc3b02659 100644 --- a/hw/ppc/spapr_pci.c +++ b/hw/ppc/spapr_pci.c @@ -2093,14 +2093,13 @@ static int spapr_pci_pre_save(void *opaque) return 0; } -static int spapr_pci_post_save(void *opaque) +static void spapr_pci_post_save(void *opaque) { SpaprPhbState *sphb = opaque; g_free(sphb->msi_devs); sphb->msi_devs = NULL; sphb->msi_devs_num = 0; - return 0; } static int spapr_pci_post_load(void *opaque, int version_id) diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h index 3695afd483..15578b3e28 100644 --- a/include/migration/vmstate.h +++ b/include/migration/vmstate.h @@ -223,7 +223,15 @@ struct VMStateDescription { bool (*post_load_errp)(void *opaque, int version_id, Error **errp); int (*pre_save)(void *opaque); bool (*pre_save_errp)(void *opaque, Error **errp); - int (*post_save)(void *opaque); + + /* + * post_save() rarely used to free some temporary resources. + * It's is called if .pre_save[_errp]() call was successful + * (or .pre_save[_errp] handler absent), regardless success + * or failure during fields and subsections save. If + * .pre_save[_errp]() fails, .post_save() is not called. + */ + void (*post_save)(void *opaque); bool (*needed)(void *opaque); bool (*dev_unplug_pending)(void *opaque); diff --git a/migration/savevm.c b/migration/savevm.c index 3a16c467b2..c5236e71ba 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -321,14 +321,13 @@ static int configuration_pre_save(void *opaque) return 0; } -static int configuration_post_save(void *opaque) +static void configuration_post_save(void *opaque) { SaveState *state = opaque; g_free(state->capabilities); state->capabilities = NULL; state->caps_count = 0; - return 0; } static int configuration_pre_load(void *opaque) diff --git a/migration/vmstate.c b/migration/vmstate.c index 651c3fe011..5111e7a141 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -550,10 +550,7 @@ static int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, if (ret) { error_prepend(errp, "Save of field %s/%s failed: ", vmsd->name, field->name); - if (vmsd->post_save) { - vmsd->post_save(opaque); - } - return ret; + goto out; } /* Compressed arrays only care about the first element */ @@ -578,12 +575,9 @@ static int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp); +out: if (vmsd->post_save) { - int ps_ret = vmsd->post_save(opaque); - if (!ret && ps_ret) { - ret = ps_ret; - error_setg(errp, "post-save failed: %s", vmsd->name); - } + vmsd->post_save(opaque); } return ret; } diff --git a/target/arm/machine.c b/target/arm/machine.c index bbaae34449..de810220e2 100644 --- a/target/arm/machine.c +++ b/target/arm/machine.c @@ -993,15 +993,13 @@ static int cpu_pre_save(void *opaque) return 0; } -static int cpu_post_save(void *opaque) +static void cpu_post_save(void *opaque) { ARMCPU *cpu = opaque; if (!kvm_enabled()) { pmu_op_finish(&cpu->env); } - - return 0; } static int cpu_pre_load(void *opaque) -- 2.52.0 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2 03/16] migration: make .post_save() a void function 2026-02-20 21:02 ` [PATCH v2 03/16] migration: make .post_save() a void function Vladimir Sementsov-Ogievskiy @ 2026-02-27 22:41 ` Fabiano Rosas 2026-02-27 23:56 ` Vladimir Sementsov-Ogievskiy 0 siblings, 1 reply; 4+ messages in thread From: Fabiano Rosas @ 2026-02-27 22:41 UTC (permalink / raw) To: Vladimir Sementsov-Ogievskiy, peterx Cc: vsementsov, Pierrick Bouvier, Nicholas Piggin, Harsh Prateek Bora, Peter Maydell, open list:All patches CC here, open list:sPAPR (pseries), open list:ARM TCG CPUs Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> writes: > All other handlers now have _errp() variants. Should we go this way > for .post_save()? Actually it's rather strange, when the vmstate do > successful preparations in .pre_save(), then successfully save all > sections and subsections, end then fail when all the state is > successfully transferred to the target. > > Happily, we have only three .post_save() realizations, all always > successful. Let's make this a rule. > > Also note, that we call .post_save() in two places, and handle > its (theoretical) failure inconsistently. Fix that too. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> > --- > docs/devel/migration/main.rst | 2 +- > hw/ppc/spapr_pci.c | 3 +-- > include/migration/vmstate.h | 10 +++++++++- > migration/savevm.c | 3 +-- > migration/vmstate.c | 12 +++--------- > target/arm/machine.c | 4 +--- > 6 files changed, 16 insertions(+), 18 deletions(-) > > diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst > index 234d280249..2de7050764 100644 > --- a/docs/devel/migration/main.rst > +++ b/docs/devel/migration/main.rst > @@ -439,7 +439,7 @@ The functions to do that are inside a vmstate definition, and are called: > > This function is called before we save the state of one device. > > -- ``int (*post_save)(void *opaque);`` > +- ``void (*post_save)(void *opaque);`` > > This function is called after we save the state of one device > (even upon failure, unless the call to pre_save returned an error). > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c > index ea998bdff1..1dc3b02659 100644 > --- a/hw/ppc/spapr_pci.c > +++ b/hw/ppc/spapr_pci.c > @@ -2093,14 +2093,13 @@ static int spapr_pci_pre_save(void *opaque) > return 0; > } > > -static int spapr_pci_post_save(void *opaque) > +static void spapr_pci_post_save(void *opaque) > { > SpaprPhbState *sphb = opaque; > > g_free(sphb->msi_devs); > sphb->msi_devs = NULL; > sphb->msi_devs_num = 0; > - return 0; > } > > static int spapr_pci_post_load(void *opaque, int version_id) > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > index 3695afd483..15578b3e28 100644 > --- a/include/migration/vmstate.h > +++ b/include/migration/vmstate.h > @@ -223,7 +223,15 @@ struct VMStateDescription { > bool (*post_load_errp)(void *opaque, int version_id, Error **errp); > int (*pre_save)(void *opaque); > bool (*pre_save_errp)(void *opaque, Error **errp); > - int (*post_save)(void *opaque); > + > + /* > + * post_save() rarely used to free some temporary resources. > + * It's is called if .pre_save[_errp]() call was successful > + * (or .pre_save[_errp] handler absent), regardless success > + * or failure during fields and subsections save. If > + * .pre_save[_errp]() fails, .post_save() is not called. > + */ I would not mention usage directly and maybe also simplify the language a bit. If there's doubt on the exact flow, people can read the code: /* * Unless .pre_save() fails, post_save() is called after saving * fields and subsections. It should not fail because at this point * the state has potentially already been transferred. */ > + void (*post_save)(void *opaque); > bool (*needed)(void *opaque); > bool (*dev_unplug_pending)(void *opaque); > > diff --git a/migration/savevm.c b/migration/savevm.c > index 3a16c467b2..c5236e71ba 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -321,14 +321,13 @@ static int configuration_pre_save(void *opaque) > return 0; > } > > -static int configuration_post_save(void *opaque) > +static void configuration_post_save(void *opaque) > { > SaveState *state = opaque; > > g_free(state->capabilities); > state->capabilities = NULL; > state->caps_count = 0; > - return 0; > } > > static int configuration_pre_load(void *opaque) > diff --git a/migration/vmstate.c b/migration/vmstate.c > index 651c3fe011..5111e7a141 100644 > --- a/migration/vmstate.c > +++ b/migration/vmstate.c > @@ -550,10 +550,7 @@ static int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, > if (ret) { > error_prepend(errp, "Save of field %s/%s failed: ", > vmsd->name, field->name); > - if (vmsd->post_save) { > - vmsd->post_save(opaque); > - } > - return ret; > + goto out; > } > > /* Compressed arrays only care about the first element */ > @@ -578,12 +575,9 @@ static int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, > > ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp); > > +out: > if (vmsd->post_save) { > - int ps_ret = vmsd->post_save(opaque); > - if (!ret && ps_ret) { > - ret = ps_ret; > - error_setg(errp, "post-save failed: %s", vmsd->name); > - } > + vmsd->post_save(opaque); Nice cleanup. > } > return ret; > } > diff --git a/target/arm/machine.c b/target/arm/machine.c > index bbaae34449..de810220e2 100644 > --- a/target/arm/machine.c > +++ b/target/arm/machine.c > @@ -993,15 +993,13 @@ static int cpu_pre_save(void *opaque) > return 0; > } > > -static int cpu_post_save(void *opaque) > +static void cpu_post_save(void *opaque) > { > ARMCPU *cpu = opaque; > > if (!kvm_enabled()) { > pmu_op_finish(&cpu->env); > } > - > - return 0; > } > > static int cpu_pre_load(void *opaque) ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 03/16] migration: make .post_save() a void function 2026-02-27 22:41 ` Fabiano Rosas @ 2026-02-27 23:56 ` Vladimir Sementsov-Ogievskiy 2026-03-03 15:05 ` Peter Xu 0 siblings, 1 reply; 4+ messages in thread From: Vladimir Sementsov-Ogievskiy @ 2026-02-27 23:56 UTC (permalink / raw) To: Fabiano Rosas, peterx Cc: Pierrick Bouvier, Nicholas Piggin, Harsh Prateek Bora, Peter Maydell, open list:All patches CC here, open list:sPAPR (pseries), open list:ARM TCG CPUs On 28.02.26 01:41, Fabiano Rosas wrote: >> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h >> index 3695afd483..15578b3e28 100644 >> --- a/include/migration/vmstate.h >> +++ b/include/migration/vmstate.h >> @@ -223,7 +223,15 @@ struct VMStateDescription { >> bool (*post_load_errp)(void *opaque, int version_id, Error **errp); >> int (*pre_save)(void *opaque); >> bool (*pre_save_errp)(void *opaque, Error **errp); >> - int (*post_save)(void *opaque); >> + >> + /* >> + * post_save() rarely used to free some temporary resources. >> + * It's is called if .pre_save[_errp]() call was successful >> + * (or .pre_save[_errp] handler absent), regardless success >> + * or failure during fields and subsections save. If >> + * .pre_save[_errp]() fails, .post_save() is not called. >> + */ > I would not mention usage directly and maybe also simplify the language > a bit. If there's doubt on the exact flow, people can read the code: > > /* > * Unless .pre_save() fails, post_save() is called after saving > * fields and subsections. It should not fail because at this point > * the state has potentially already been transferred. > */ Agree, sounds good. -- Best regards, Vladimir ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2 03/16] migration: make .post_save() a void function 2026-02-27 23:56 ` Vladimir Sementsov-Ogievskiy @ 2026-03-03 15:05 ` Peter Xu 0 siblings, 0 replies; 4+ messages in thread From: Peter Xu @ 2026-03-03 15:05 UTC (permalink / raw) To: Vladimir Sementsov-Ogievskiy Cc: Fabiano Rosas, Pierrick Bouvier, Nicholas Piggin, Harsh Prateek Bora, Peter Maydell, open list:All patches CC here, open list:sPAPR (pseries), open list:ARM TCG CPUs On Sat, Feb 28, 2026 at 02:56:30AM +0300, Vladimir Sementsov-Ogievskiy wrote: > On 28.02.26 01:41, Fabiano Rosas wrote: > > > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > > > index 3695afd483..15578b3e28 100644 > > > --- a/include/migration/vmstate.h > > > +++ b/include/migration/vmstate.h > > > @@ -223,7 +223,15 @@ struct VMStateDescription { > > > bool (*post_load_errp)(void *opaque, int version_id, Error **errp); > > > int (*pre_save)(void *opaque); > > > bool (*pre_save_errp)(void *opaque, Error **errp); > > > - int (*post_save)(void *opaque); > > > + > > > + /* > > > + * post_save() rarely used to free some temporary resources. > > > + * It's is called if .pre_save[_errp]() call was successful > > > + * (or .pre_save[_errp] handler absent), regardless success > > > + * or failure during fields and subsections save. If > > > + * .pre_save[_errp]() fails, .post_save() is not called. > > > + */ > > I would not mention usage directly and maybe also simplify the language > > a bit. If there's doubt on the exact flow, people can read the code: > > > > /* > > * Unless .pre_save() fails, post_save() is called after saving > > * fields and subsections. It should not fail because at this point > > * the state has potentially already been transferred. > > */ > > > Agree, sounds good. With the update, feel free to take: Reviewed-by: Peter Xu <peterx@redhat.com> -- Peter Xu ^ permalink raw reply [flat|nested] 4+ messages in thread
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2026-02-20 21:02 ` [PATCH v2 03/16] migration: make .post_save() a void function Vladimir Sementsov-Ogievskiy
2026-02-27 22:41 ` Fabiano Rosas
2026-02-27 23:56 ` Vladimir Sementsov-Ogievskiy
2026-03-03 15:05 ` Peter Xu
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