RE: [PATCH 8/9] physmem,gdbstub: Add helper functions to help *unrealize* vCPU object

[Salil Mehta]

> From: Alex Bennée <alex.bennee@linaro.org>
> Sent: Friday, September 29, 2023 3:35 PM
> To: Salil Mehta <salil.mehta@huawei.com>
> Cc: qemu-devel@nongnu.org; qemu-arm@nongnu.org; maz@kernel.org; jean-
> philippe@linaro.org; Jonathan Cameron <jonathan.cameron@huawei.com>;
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> <linuxarm@huawei.com>
> Subject: Re: [PATCH 8/9] physmem,gdbstub: Add helper functions to help
> *unrealize* vCPU object
> 
> 
> Salil Mehta <salil.mehta@huawei.com> writes:
> 
> > vCPU Hot-unplug requires some helper functions to unroll what has happened
> > during realization of a CPU object.
> >
> > Signed-off-by: Salil Mehta <salil.mehta@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/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
> > index 349d348c7b..a06ea3adad 100644
> > --- a/gdbstub/gdbstub.c
> > +++ b/gdbstub/gdbstub.c
> > @@ -491,6 +491,19 @@ void gdb_register_coprocessor(CPUState *cpu,
> >      }
> >  }
> >
> > +void gdb_unregister_coprocessor_all(CPUState *cpu)
> > +{
> > +    GDBRegisterState *s, *p;
> > +
> > +    p = cpu->gdb_regs;
> > +    while (p) {
> > +        s = p;
> > +        p = p->next;
> 
> Maybe add:
> 
>       /* s->xml is static const char so isn't freed */


Sure.

> > +        g_free(s);
> > +    }
> > +    cpu->gdb_regs = NULL;
> > +}
> > +
> >  static void gdb_process_breakpoint_remove_all(GDBProcess *p)
> >  {
> >      CPUState *cpu = gdb_get_first_cpu_in_process(p);
> > diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> > index 41788c0bdd..eb56a228a2 100644
> > --- a/include/exec/cpu-common.h
> > +++ b/include/exec/cpu-common.h
> > @@ -120,6 +120,14 @@ size_t qemu_ram_pagesize_largest(void);
> >   */
> >  void cpu_address_space_init(CPUState *cpu, int asidx,
> >                              const char *prefix, MemoryRegion *mr);
> > +/**
> > + * cpu_address_space_destroy:
> > + * @cpu: CPU for which address space needs to be destroyed
> > + * @asidx: integer index of this address space
> > + *
> > + * Note that with KVM only one address space is supported.
> > + */
> > +void cpu_address_space_destroy(CPUState *cpu, int asidx);
> >
> >  void cpu_physical_memory_rw(hwaddr addr, void *buf,
> >                              hwaddr len, bool is_write);
> > diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
> > index 16a139043f..986d8d2fa5 100644
> > --- a/include/exec/gdbstub.h
> > +++ b/include/exec/gdbstub.h
> > @@ -27,6 +27,7 @@ typedef int (*gdb_set_reg_cb)(CPUArchState *env, uint8_t 
> > *buf, int reg);
> >  void gdb_register_coprocessor(CPUState *cpu,
> >                                gdb_get_reg_cb get_reg, gdb_set_reg_cb 
> > set_reg,
> >                                int num_regs, const char *xml, int 
> >  g_pos);
> 
> Can we have a kdoc comment here describing the function.

Ok.

> 
> I suspect this should be split into two patches, one for gdbstub and one
> for physmem.


No issues. Can do that.


> > +void gdb_unregister_coprocessor_all(CPUState *cpu);
> >
> >  /**
> >   * gdbserver_start: start the gdb server
> > diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> > index 648b5b3586..65d2ae4581 100644
> > --- a/include/hw/core/cpu.h
> > +++ b/include/hw/core/cpu.h
> > @@ -355,6 +355,7 @@ struct CPUState {
> >      QSIMPLEQ_HEAD(, qemu_work_item) work_list;
> >
> >      CPUAddressSpace *cpu_ases;
> > +    int cpu_ases_count;
> >      int num_ases;
> >      AddressSpace *as;
> >      MemoryRegion *memory;
> > diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> > index 4f6ca653b3..4dfa0ca66f 100644
> > --- a/softmmu/physmem.c
> > +++ b/softmmu/physmem.c
> > @@ -761,6 +761,7 @@ 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_count = cpu->num_ases;
> >      }
> >
> >      newas = &cpu->cpu_ases[asidx];
> > @@ -774,6 +775,30 @@ 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_count == 1) {
> > +        g_free(cpu->cpu_ases);
> > +        cpu->cpu_ases = NULL;
> > +    }
> > +
> > +    cpu->cpu_ases_count--;
> > +}
> > +
> >  AddressSpace *cpu_get_address_space(CPUState *cpu, int asidx)
> >  {
> >      /* Return the AddressSpace corresponding to the specified index */
> 
> 
> --
> Alex Bennée
> Virtualisation Tech Lead @ Linaro