On Mon, Mar 23, 2015 at 07:05:55PM +0530, Bharata B Rao 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. > > Signed-off-by: Bharata B Rao <[email protected]> > --- > exec.c | 37 ++++++++++++++++++++++++++++++++++--- > include/qom/cpu.h | 8 ++++++++ > 2 files changed, 42 insertions(+), 3 deletions(-) > > diff --git a/exec.c b/exec.c > index e1ff6b0..9bbab02 100644 > --- a/exec.c > +++ b/exec.c > @@ -527,21 +527,52 @@ 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); > + return max_cpus; > + } else { > + bitmap_set(cpu_index_map, cpu, 1); > + return cpu; > + } > +} > + > +void cpu_exec_exit(CPUState *cpu) > +{ > + bitmap_clear(cpu_index_map, cpu->cpu_index, 1); > +}
AFAICT, this function is never called, which seems like a bug.
> +#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;
> -
> #if defined(CONFIG_USER_ONLY)
> + CPUState *some_cpu;
> +
> cpu_list_lock();
> -#endif
> cpu_index = 0;
> CPU_FOREACH(some_cpu) {
> cpu_index++;
> }
> cpu->cpu_index = cpu_index;
> +#else
> + Error *local_err = NULL;
> +
> + cpu_index = cpu->cpu_index = cpu_get_free_index(&local_err);
> + if (local_err) {
> + error_propagate(errp, local_err);
> + return;
> + }
> +#endif
> 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 48fd6fb..5241cf4 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -659,6 +659,14 @@ void cpu_watchpoint_remove_all(CPUState *cpu, int mask);
> void QEMU_NORETURN cpu_abort(CPUState *cpu, const char *fmt, ...)
> GCC_FMT_ATTR(2, 3);
>
> +#ifndef CONFIG_USER_ONLY
> +void cpu_exec_exit(CPUState *cpu);
> +#else
> +static inline void cpu_exec_exit(CPUState *cpu)
> +{
> +}
> +#endif
> +
> #ifdef CONFIG_SOFTMMU
> extern const struct VMStateDescription vmstate_cpu_common;
> #else
--
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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