Hi Phil,
> From: Philippe Mathieu-Daudé <phi...@linaro.org>
> Sent: Tuesday, October 3, 2023 7:34 AM
> To: Salil Mehta <salil.me...@huawei.com>; qemu-devel@nongnu.org; qemu-
> a...@nongnu.org
> Cc: m...@kernel.org; jean-phili...@linaro.org; Jonathan Cameron
> <jonathan.came...@huawei.com>; lpieral...@kernel.org;
> peter.mayd...@linaro.org; richard.hender...@linaro.org;
> imamm...@redhat.com; andrew.jo...@linux.dev; da...@redhat.com;
> eric.au...@redhat.com; w...@kernel.org; a...@kernel.org;
> oliver.up...@linux.dev; pbonz...@redhat.com; m...@redhat.com;
> gs...@redhat.com; raf...@kernel.org; borntrae...@linux.ibm.com;
> alex.ben...@linaro.org; li...@armlinux.org.uk;
> dar...@os.amperecomputing.com; il...@os.amperecomputing.com;
> vis...@os.amperecomputing.com; karl.heub...@oracle.com;
> miguel.l...@oracle.com; salil.me...@opnsrc.net; zhukeqian
> <zhukeqi...@huawei.com>; wangxiongfeng (C) <wangxiongfe...@huawei.com>;
> wangyanan (Y) <wangyana...@huawei.com>; jiakern...@gmail.com;
> maob...@loongson.cn; lixiang...@loongson.cn
> Subject: Re: [PATCH RFC V2 31/37] physmem,gdbstub: Common helping
> funcs/changes to *unrealize* vCPU
>
> Hi Salil,
>
> On 26/9/23 12:04, Salil Mehta wrote:
> > Supporting vCPU Hotplug for ARM arch also means introducing new
> functionality of
> > unrealizing the ARMCPU. This requires some new common functions.
> >
> > Defining them as part of architecture independent change so that this
> code could
> > be reused by other interested parties.
> >
> > Signed-off-by: Salil Mehta <salil.me...@huawei.com>
> > ---
> > gdbstub/gdbstub.c | 13 +++++++++++++
> > include/exec/cpu-common.h | 8 ++++++++
> > include/exec/gdbstub.h | 1 +
> > include/hw/core/cpu.h | 1 +
> > softmmu/physmem.c | 25 +++++++++++++++++++++++++
> > 5 files changed, 48 insertions(+)
>
>
> > diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> > index dab572c9bd..ffd815a0d8 100644
> > --- a/include/hw/core/cpu.h
> > +++ b/include/hw/core/cpu.h
> > @@ -366,6 +366,7 @@ struct CPUState {
> > QSIMPLEQ_HEAD(, qemu_work_item) work_list;
> >
> > CPUAddressSpace *cpu_ases;
> > + int cpu_ases_ref_count;
> > int num_ases;
> > AddressSpace *as;
> > MemoryRegion *memory;
> > diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> > index 3df73542e1..a93ae783af 100644
> > --- a/softmmu/physmem.c
> > +++ b/softmmu/physmem.c
> > @@ -762,6 +762,7 @@ void cpu_address_space_init(CPUState *cpu, int asidx,
> >
> > if (!cpu->cpu_ases) {
> > cpu->cpu_ases = g_new0(CPUAddressSpace, cpu->num_ases);
> > + cpu->cpu_ases_ref_count = cpu->num_ases;
> > }
> >
> > newas = &cpu->cpu_ases[asidx];
> > @@ -775,6 +776,30 @@ void cpu_address_space_init(CPUState *cpu, int
> asidx,
> > }
> > }
> >
> > +void cpu_address_space_destroy(CPUState *cpu, int asidx)
> > +{
> > + CPUAddressSpace *cpuas;
> > +
> > + assert(asidx < cpu->num_ases);
> > + assert(asidx == 0 || !kvm_enabled());
> > + assert(cpu->cpu_ases);
> > +
> > + cpuas = &cpu->cpu_ases[asidx];
> > + if (tcg_enabled()) {
> > + memory_listener_unregister(&cpuas->tcg_as_listener);
> > + }
> > +
> > + address_space_destroy(cpuas->as);
> > + g_free_rcu(cpuas->as, rcu);
> > +
> > + if (cpu->cpu_ases_ref_count == 1) {
> > + g_free(cpu->cpu_ases);
> > + cpu->cpu_ases = NULL;
> > + }
> > +
> > + cpu->cpu_ases_ref_count--;
>
> See Richard comment from:
> https://lore.kernel.org/qemu-devel/594b2550-9a73-684f-6e54-
> 29401dc6c...@linaro.org/
>
> "I think it would be better to destroy all address spaces at once,
> "so that you don't need to invent a reference count that isn't used
> "for anything else.
Yes, we can do that and remove the reference count. The only reason I
did it was because I was not sure if it is safe to assume that all
the AddressSpace will always be destroyed *together*. And now since
this is being ported to other architectures will the same hold
true everywhere?
Thanks
Salil.
