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Re: [Qemu-devel] [RFC PATCH v2 14/23] cpus: Convert cpu_index into a bit
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 14/23] cpus: Convert cpu_index into a bitmap |
Date: |
Wed, 25 Mar 2015 14:23:29 +1100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
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 <address@hidden>
> ---
> 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
pgpjs7IrPl2iv.pgp
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- [Qemu-devel] [RFC PATCH v2 11/23] ppc: Create sockets and cores for CPUs, (continued)
- [Qemu-devel] [RFC PATCH v2 13/23] cpus: Add Error argument to cpu_exec_init(), Bharata B Rao, 2015/03/23
- [Qemu-devel] [RFC PATCH v2 15/23] ppc: Move cpu_exec_init() call to realize function, Bharata B Rao, 2015/03/23
- [Qemu-devel] [RFC PATCH v2 14/23] cpus: Convert cpu_index into a bitmap, Bharata B Rao, 2015/03/23
- Re: [Qemu-devel] [RFC PATCH v2 14/23] cpus: Convert cpu_index into a bitmap,
David Gibson <=
- [Qemu-devel] [RFC PATCH v2 16/23] cpus: Reclaim vCPU objects, Bharata B Rao, 2015/03/23
- [Qemu-devel] [RFC PATCH v2 17/23] xics_kvm: Don't enable KVM_CAP_IRQ_XICS if already enabled, Bharata B Rao, 2015/03/23
[Qemu-devel] [RFC PATCH v2 18/23] xics_kvm: Add cpu_destroy method to XICS, Bharata B Rao, 2015/03/23
[Qemu-devel] [RFC PATCH v2 20/23] spapr: Remove vCPU objects after CPU hot unplug, Bharata B Rao, 2015/03/23