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Re: [Qemu-devel] [PATCH] spapr_cpu_core: instantiate CPUs separately
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH] spapr_cpu_core: instantiate CPUs separately |
Date: |
Sat, 14 Oct 2017 20:33:37 +1100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Oct 13, 2017 at 01:31:44PM +0200, Greg Kurz wrote:
> The current code assumes that only the CPU core object holds a
> reference on each individual CPU object, and happily frees their
> allocated memory when the core is unrealized. This is dangerous
> as some other code can legitimely keep a pointer to a CPU if it
> calls object_ref(), but it would end up with a dangling pointer.
>
> Let's allocate all CPUs with object_new() and let QOM frees them
> when their reference count reaches zero. This greatly simplify the
> code as we don't have to fiddle with the instance size anymore.
>
> Signed-off-by: Greg Kurz <address@hidden>
So, I'm pretty sure my first drafts of the core stuff did things this
waym and it got nacked, for QOM lifetime reasons that I never really
understood.
> ---
> v2: - mention code simplification in changelog
> - use PowerPCCPU * and Object * instead of void *
> ---
> hw/ppc/spapr.c | 11 +++--------
> hw/ppc/spapr_cpu_core.c | 19 +++++++------------
> include/hw/ppc/spapr_cpu_core.h | 2 +-
> 3 files changed, 11 insertions(+), 21 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index fd9813bde82f..d9555a3677be 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3153,12 +3153,10 @@ void spapr_core_release(DeviceState *dev)
>
> if (smc->pre_2_10_has_unused_icps) {
> sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> - sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(cc));
> - size_t size = object_type_get_instance_size(scc->cpu_type);
> int i;
>
> for (i = 0; i < cc->nr_threads; i++) {
> - CPUState *cs = CPU(sc->threads + i * size);
> + CPUState *cs = CPU(sc->threads[i]);
>
> pre_2_10_vmstate_register_dummy_icp(cs->cpu_index);
> }
> @@ -3204,7 +3202,7 @@ static void spapr_core_plug(HotplugHandler
> *hotplug_dev, DeviceState *dev,
> sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
> sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> CPUCore *cc = CPU_CORE(dev);
> - CPUState *cs = CPU(core->threads);
> + CPUState *cs = CPU(core->threads[0]);
> sPAPRDRConnector *drc;
> Error *local_err = NULL;
> int smt = kvmppc_smt_threads();
> @@ -3249,15 +3247,12 @@ static void spapr_core_plug(HotplugHandler
> *hotplug_dev, DeviceState *dev,
> core_slot->cpu = OBJECT(dev);
>
> if (smc->pre_2_10_has_unused_icps) {
> - sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(cc));
> - size_t size = object_type_get_instance_size(scc->cpu_type);
> int i;
>
> for (i = 0; i < cc->nr_threads; i++) {
> sPAPRCPUCore *sc = SPAPR_CPU_CORE(dev);
> - void *obj = sc->threads + i * size;
>
> - cs = CPU(obj);
> + cs = CPU(sc->threads[i]);
> pre_2_10_vmstate_unregister_dummy_icp(cs->cpu_index);
> }
> }
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 3a4c17401226..588f9b45714a 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -79,13 +79,11 @@ const char *spapr_get_cpu_core_type(const char *cpu_type)
> static void spapr_cpu_core_unrealizefn(DeviceState *dev, Error **errp)
> {
> sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> - sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(dev));
> - size_t size = object_type_get_instance_size(scc->cpu_type);
> CPUCore *cc = CPU_CORE(dev);
> int i;
>
> for (i = 0; i < cc->nr_threads; i++) {
> - void *obj = sc->threads + i * size;
> + Object *obj = OBJECT(sc->threads[i]);
> DeviceState *dev = DEVICE(obj);
> CPUState *cs = CPU(dev);
> PowerPCCPU *cpu = POWERPC_CPU(cs);
> @@ -146,9 +144,8 @@ static void spapr_cpu_core_realize(DeviceState *dev,
> Error **errp)
> sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(OBJECT(dev));
> CPUCore *cc = CPU_CORE(OBJECT(dev));
> - size_t size;
> Error *local_err = NULL;
> - void *obj;
> + Object *obj;
> int i, j;
>
> if (!spapr) {
> @@ -156,18 +153,16 @@ static void spapr_cpu_core_realize(DeviceState *dev,
> Error **errp)
> return;
> }
>
> - size = object_type_get_instance_size(scc->cpu_type);
> - sc->threads = g_malloc0(size * cc->nr_threads);
> + sc->threads = g_new(PowerPCCPU *, cc->nr_threads);
> for (i = 0; i < cc->nr_threads; i++) {
> char id[32];
> CPUState *cs;
> PowerPCCPU *cpu;
>
> - obj = sc->threads + i * size;
> + obj = object_new(scc->cpu_type);
>
> - object_initialize(obj, size, scc->cpu_type);
> cs = CPU(obj);
> - cpu = POWERPC_CPU(cs);
> + cpu = sc->threads[i] = POWERPC_CPU(obj);
> cs->cpu_index = cc->core_id + i;
> cpu->vcpu_id = (cc->core_id * spapr->vsmt / smp_threads) + i;
> if (kvm_enabled() && !kvm_vcpu_id_is_valid(cpu->vcpu_id)) {
> @@ -192,7 +187,7 @@ static void spapr_cpu_core_realize(DeviceState *dev,
> Error **errp)
> }
>
> for (j = 0; j < cc->nr_threads; j++) {
> - obj = sc->threads + j * size;
> + obj = OBJECT(sc->threads[j]);
>
> spapr_cpu_core_realize_child(obj, spapr, &local_err);
> if (local_err) {
> @@ -203,7 +198,7 @@ static void spapr_cpu_core_realize(DeviceState *dev,
> Error **errp)
>
> err:
> while (--i >= 0) {
> - obj = sc->threads + i * size;
> + obj = OBJECT(sc->threads[i]);
> object_unparent(obj);
> }
> g_free(sc->threads);
> diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
> index f2d48d6a6786..1129f344aa0c 100644
> --- a/include/hw/ppc/spapr_cpu_core.h
> +++ b/include/hw/ppc/spapr_cpu_core.h
> @@ -28,7 +28,7 @@ typedef struct sPAPRCPUCore {
> CPUCore parent_obj;
>
> /*< public >*/
> - void *threads;
> + PowerPCCPU **threads;
> int node_id;
> } sPAPRCPUCore;
>
>
--
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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