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Re: [Qemu-devel] [RFC v0 PATCH] cpus: Convert cpu_index into a bitmap
From: |
Bharata B Rao |
Subject: |
Re: [Qemu-devel] [RFC v0 PATCH] cpus: Convert cpu_index into a bitmap |
Date: |
Thu, 7 May 2015 15:05:45 +0530 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Wed, Mar 18, 2015 at 11:50:04AM +0530, Bharata B Rao wrote:
> On Tue, Mar 17, 2015 at 11:56:04AM +0100, Andreas Färber wrote:
> > Am 17.03.2015 um 09:39 schrieb Bharata B Rao:
> > > On Tue, Mar 17, 2015 at 07:56:41AM +0100, Alexander Graf wrote:
> > >>
> > >>
> > >> On 13.03.15 12:56, Bharata B Rao wrote:
> > >>> From: Bharata B Rao <address@hidden>
> > >>>
> > >>> 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 <address@hidden>
> > >>> ---
> > >>> 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?
> > >
> > > Yes possible and that would be much cleaner since I wouldn't have to touch
> > > all archs. But it will be asymmetric in some sense as cpu_exec_init() is
> > > called from all individual cpus' instance_init but cpu_exec_exit() will be
> > > called from parent's (TYPE_CPU) instance_finalize. If that is fine, I
> > > shall
> > > post v2 with this change.
> >
> > Could you check: Wasn't there a patch from Fujitsu to move
> > cpu_exec_init() to generic code? If both were generic, that would be
> > fine. If that is problematic, I would accept the mismatch as long as it
> > is "safe". That is, instance_finalize needs to handle any state of the
> > object,
>
> There is a patch from Zhu to move only vmstate_register related bits
> from cpu_exec_init to cpu_common_realizefn.
>
> http://lists.gnu.org/archive/html/qemu-devel/2015-01/msg01550.html
>
> > and I think these two are better suited for realize/unrealize
> > than instance_init/instance_finalize.
>
> And Eduardo has a patch to move cpu_exec_init call from instance_init
> to realize for target-i386.
>
> https://lists.gnu.org/archive/html/qemu-devel/2015-03/msg01056.html
>
> So if the preferred way is to call cpu_exec_init from realize, then
> Eduardo - Can you do this for all archs ? My limited testing shows
> that it (moving cpu_exec_init from instance_init to realize) works for
> sPAPR PowerPC too, but not sure about other targets.
>
> After there is consensus on the above two patches, I can do the
> cpu_index to bitmap changes.
I was planning to re-post this patch now, but wanted to know the plan
regarding the related two patchsets that I have mentioned above.
1. Patch by Eduardo to move cpu_exec_init from instance_init to realizefn
2. Patch by Zhu to move vmstate_register related bits from cpu_exec_init
to cpu_common_realizefn.
I don't see any more updates on this, are these obsolete or still under
consideration ?
Regards,
Bharata.
- Re: [Qemu-devel] [RFC v0 PATCH] cpus: Convert cpu_index into a bitmap,
Bharata B Rao <=