On Thu, 21 May 2015 10:32:07 +0530 Bharata B Rao <bhar...@linux.vnet.ibm.com> wrote:
> Currently CPUState.cpu_index is monotonically increasing and a newly > created CPU always gets the next higher index. The next available > index is calculated by counting the existing number of CPUs. This is > fine as long as we only add CPUs, but there are architectures which > are starting to support CPU removal too. For an architecture like PowerPC > which derives its CPU identifier (device tree ID) from cpu_index, the > existing logic of generating cpu_index values causes problems. > > With the currently proposed method of handling vCPU removal by parking > the vCPU fd in QEMU > (Ref: http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg02604.html), > generating cpu_index this way will not work for PowerPC. > > This patch changes the way cpu_index is handed out by maintaining > a bit map of the CPUs that tracks both addition and removal of CPUs. > > The CPU bitmap allocation logic is part of cpu_exec_init() which is > called by instance_init routines of various CPU targets. Newly added > cpu_exec_exit() API handles the deallocation part and this routine is > called from generic CPU::instance_finalize(). > > Note: This new CPU enumeration is for !CONFIG_USER_ONLY only. > CONFIG_USER_ONLY continues to have the old enumeration logic. > > Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> > Reviewed-by: Eduardo Habkost <ehabk...@redhat.com> minor nit below, otherwise: Reviewed-by: Igor Mammedov <imamm...@redhat.com> > --- > exec.c | 55 > ++++++++++++++++++++++++++++++++++++++++++++++++++----- > include/qom/cpu.h | 1 + > qom/cpu.c | 7 +++++++ > 3 files changed, 58 insertions(+), 5 deletions(-) > > diff --git a/exec.c b/exec.c > index 5cf821e..dd688b8 100644 > --- a/exec.c > +++ b/exec.c > @@ -518,21 +518,66 @@ void tcg_cpu_address_space_init(CPUState *cpu, > AddressSpace *as) > } > #endif > > +#ifndef CONFIG_USER_ONLY > +static DECLARE_BITMAP(cpu_index_map, MAX_CPUMASK_BITS); > + > +static int cpu_get_free_index(Error **errp) > +{ > + int cpu = find_first_zero_bit(cpu_index_map, max_cpus); > + > + if (cpu >= max_cpus) { > + error_setg(errp, "Trying to use more CPUs than allowed max of %d\n", > + max_cpus); wrong indent > + return -1; > + } > + > + bitmap_set(cpu_index_map, cpu, 1); > + return cpu; > +} > + > +void cpu_exec_exit(CPUState *cpu) > +{ > + if (cpu->cpu_index == -1) { > + /* cpu_index was never allocated by this @cpu or was already freed. > */ > + return; > + } > + > + bitmap_clear(cpu_index_map, cpu->cpu_index, 1); > + cpu->cpu_index = -1; > +} > +#else > + > +static int cpu_get_free_index(Error **errp) > +{ > + CPUState *some_cpu; > + int cpu_index = 0; > + > + CPU_FOREACH(some_cpu) { > + cpu_index++; > + } > + return cpu_index; > +} > + > +void cpu_exec_exit(CPUState *cpu) > +{ > +} > +#endif > + > void cpu_exec_init(CPUArchState *env, Error **errp) > { > CPUState *cpu = ENV_GET_CPU(env); > CPUClass *cc = CPU_GET_CLASS(cpu); > - CPUState *some_cpu; > int cpu_index; > + Error *local_err = NULL; > > #if defined(CONFIG_USER_ONLY) > cpu_list_lock(); > #endif > - cpu_index = 0; > - CPU_FOREACH(some_cpu) { > - cpu_index++; > + cpu_index = cpu->cpu_index = cpu_get_free_index(&local_err); > + if (local_err) { > + error_propagate(errp, local_err); > + return; > } > - cpu->cpu_index = cpu_index; > cpu->numa_node = 0; > QTAILQ_INIT(&cpu->breakpoints); > QTAILQ_INIT(&cpu->watchpoints); > diff --git a/include/qom/cpu.h b/include/qom/cpu.h > index 39f0f19..7db310e 100644 > --- a/include/qom/cpu.h > +++ b/include/qom/cpu.h > @@ -672,6 +672,7 @@ void cpu_watchpoint_remove_all(CPUState *cpu, int mask); > > void QEMU_NORETURN cpu_abort(CPUState *cpu, const char *fmt, ...) > GCC_FMT_ATTR(2, 3); > +void cpu_exec_exit(CPUState *cpu); > > #ifdef CONFIG_SOFTMMU > extern const struct VMStateDescription vmstate_cpu_common; > diff --git a/qom/cpu.c b/qom/cpu.c > index 108bfa2..061a0c3 100644 > --- a/qom/cpu.c > +++ b/qom/cpu.c > @@ -312,9 +312,15 @@ static void cpu_common_initfn(Object *obj) > CPUState *cpu = CPU(obj); > CPUClass *cc = CPU_GET_CLASS(obj); > > + cpu->cpu_index = -1; > cpu->gdb_num_regs = cpu->gdb_num_g_regs = cc->gdb_num_core_regs; > } > > +static void cpu_common_finalize(Object *obj) > +{ > + cpu_exec_exit(CPU(obj)); > +} > + > static int64_t cpu_common_get_arch_id(CPUState *cpu) > { > return cpu->cpu_index; > @@ -356,6 +362,7 @@ static const TypeInfo cpu_type_info = { > .parent = TYPE_DEVICE, > .instance_size = sizeof(CPUState), > .instance_init = cpu_common_initfn, > + .instance_finalize = cpu_common_finalize, > .abstract = true, > .class_size = sizeof(CPUClass), > .class_init = cpu_class_init,
