From: Alexander Graf <agraf@suse.de>
To: Bharata B Rao <bharata@linux.vnet.ibm.com>, qemu-devel@nongnu.org
Cc: imammedo@redhat.com, zhugh.fnst@cn.fujitsu.com,
Bharata B Rao <bharata.rao@gmail.com>,
afaerber@suse.de, david@gibson.dropbear.id.au
Subject: Re: [Qemu-devel] [RFC v0 PATCH] cpus: Convert cpu_index into a bitmap
Date: Tue, 17 Mar 2015 07:56:41 +0100 [thread overview]
Message-ID: <5507D029.8040608@suse.de> (raw)
In-Reply-To: <1426247796-1657-1-git-send-email-bharata@linux.vnet.ibm.com>
On 13.03.15 12:56, Bharata B Rao wrote:
> From: Bharata B Rao <bharata.rao@gmail.com>
>
> 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.
>
> I am not sure if this is the right and an acceptable approach. The
> alternative is to do something similar for PowerPC alone and not
> depend on cpu_index.
>
> I have tested this with out-of-the-tree patches for CPU hot plug and
> removal on x86 and sPAPR PowerPC.
>
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
> exec.c | 39 +++++++++++++++++++++++++++++----------
> include/exec/exec-all.h | 1 +
> target-alpha/cpu.c | 6 ++++++
> target-arm/cpu.c | 1 +
> target-cris/cpu.c | 6 ++++++
> target-i386/cpu.c | 6 ++++++
> target-lm32/cpu.c | 6 ++++++
> target-m68k/cpu.c | 6 ++++++
> target-microblaze/cpu.c | 6 ++++++
> target-mips/cpu.c | 6 ++++++
> target-moxie/cpu.c | 6 ++++++
> target-openrisc/cpu.c | 6 ++++++
> target-ppc/translate_init.c | 6 ++++++
> target-s390x/cpu.c | 1 +
> target-sh4/cpu.c | 6 ++++++
> target-sparc/cpu.c | 1 +
> target-tricore/cpu.c | 5 +++++
> target-unicore32/cpu.c | 6 ++++++
> target-xtensa/cpu.c | 6 ++++++
> 19 files changed, 116 insertions(+), 10 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index e97071a..7760f2d 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -530,21 +530,40 @@ void tcg_cpu_address_space_init(CPUState *cpu, AddressSpace *as)
> }
> #endif
>
> +static DECLARE_BITMAP(cpu_index_map, MAX_CPUMASK_BITS);
> +
> +#ifdef CONFIG_USER_ONLY
> +int max_cpus = 1; /* TODO: Check if this is correct ? */
> +#endif
> +
> +static int cpu_get_free_index(void)
> +{
> + int cpu = find_first_zero_bit(cpu_index_map, max_cpus);
> +
> + if (cpu == max_cpus) {
> + fprintf(stderr, "WARNING: qemu: 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);
> +}
> +
> void cpu_exec_init(CPUArchState *env)
> {
> CPUState *cpu = ENV_GET_CPU(env);
> CPUClass *cc = CPU_GET_CLASS(cpu);
> - CPUState *some_cpu;
> - int cpu_index;
>
> #if defined(CONFIG_USER_ONLY)
> cpu_list_lock();
> #endif
> - cpu_index = 0;
> - CPU_FOREACH(some_cpu) {
> - cpu_index++;
> - }
> - cpu->cpu_index = cpu_index;
> + cpu->cpu_index = cpu_get_free_index();
> cpu->numa_node = 0;
> QTAILQ_INIT(&cpu->breakpoints);
> QTAILQ_INIT(&cpu->watchpoints);
> @@ -558,16 +577,16 @@ void cpu_exec_init(CPUArchState *env)
> cpu_list_unlock();
> #endif
> if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
> - vmstate_register(NULL, cpu_index, &vmstate_cpu_common, cpu);
> + vmstate_register(NULL, cpu->cpu_index, &vmstate_cpu_common, cpu);
> }
> #if defined(CPU_SAVE_VERSION) && !defined(CONFIG_USER_ONLY)
> - register_savevm(NULL, "cpu", cpu_index, CPU_SAVE_VERSION,
> + register_savevm(NULL, "cpu", cpu->cpu_index, CPU_SAVE_VERSION,
> cpu_save, cpu_load, env);
> assert(cc->vmsd == NULL);
> assert(qdev_get_vmsd(DEVICE(cpu)) == NULL);
> #endif
> if (cc->vmsd != NULL) {
> - vmstate_register(NULL, cpu_index, cc->vmsd, cpu);
> + vmstate_register(NULL, cpu->cpu_index, cc->vmsd, cpu);
> }
> }
>
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 8eb0db3..95fbba0 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -89,6 +89,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> target_ulong pc, target_ulong cs_base, int flags,
> int cflags);
> void cpu_exec_init(CPUArchState *env);
> +void cpu_exec_exit(CPUState *cpu);
> void QEMU_NORETURN cpu_loop_exit(CPUState *cpu);
> int page_unprotect(target_ulong address, uintptr_t pc, void *puc);
> void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
> diff --git a/target-alpha/cpu.c b/target-alpha/cpu.c
> index a98b7d8..7c57165 100644
> --- a/target-alpha/cpu.c
> +++ b/target-alpha/cpu.c
> @@ -250,6 +250,11 @@ static const TypeInfo ev68_cpu_type_info = {
> .parent = TYPE("ev67"),
> };
>
> +static void alpha_cpu_finalize(Object *obj)
> +{
> + cpu_exec_exit(CPU(obj));
> +}
> +
> static void alpha_cpu_initfn(Object *obj)
> {
> CPUState *cs = CPU(obj);
> @@ -305,6 +310,7 @@ static const TypeInfo alpha_cpu_type_info = {
> .parent = TYPE_CPU,
> .instance_size = sizeof(AlphaCPU),
> .instance_init = alpha_cpu_initfn,
> + .instance_finalize = alpha_cpu_finalize,
Would it be possible to put this into TYPE_CPU->instance_finalize instead?
Alex
next prev parent reply other threads:[~2015-03-17 6:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-13 11:56 [Qemu-devel] [RFC v0 PATCH] cpus: Convert cpu_index into a bitmap Bharata B Rao
2015-03-17 6:56 ` Alexander Graf [this message]
2015-03-17 8:39 ` Bharata B Rao
2015-03-17 10:56 ` Andreas Färber
2015-03-18 6:20 ` Bharata B Rao
2015-03-19 13:58 ` Eduardo Habkost
2015-05-07 9:35 ` Bharata B Rao
2015-05-07 15:33 ` Eduardo Habkost
2015-03-17 10:51 ` Andreas Färber
2015-03-18 6:28 ` Bharata B Rao
2015-03-18 0:49 ` David Gibson
2015-03-18 6:34 ` Bharata B Rao
2015-03-19 4:43 ` David Gibson
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