Re: [PATCH V13 6/8] physmem: Add helper function to destroy CPU AddressSpace

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 7 Jun 2024 12:56:47 +0100
Salil Mehta <salil.mehta@huawei.com> wrote:

> Virtual CPU Hot-unplug leads to unrealization of a CPU object. This also
> involves destruction of the CPU AddressSpace. Add common function to help
> destroy the CPU AddressSpace.
> 
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Xianglai Li <lixianglai@loongson.cn>
> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> Tested-by: Zhao Liu <zhao1.liu@intel.com>


Acked-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  include/exec/cpu-common.h |  8 ++++++++
>  include/hw/core/cpu.h     |  1 +
>  system/physmem.c          | 29 +++++++++++++++++++++++++++++
>  3 files changed, 38 insertions(+)
> 
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index 815342d043..240ee04369 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -129,6 +129,14 @@ 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/hw/core/cpu.h b/include/hw/core/cpu.h
> index bb398e8237..60b160d0b4 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -486,6 +486,7 @@ struct CPUState {
>      QSIMPLEQ_HEAD(, qemu_work_item) work_list;
>  
>      struct CPUAddressSpace *cpu_ases;
> +    int cpu_ases_count;
>      int num_ases;
>      AddressSpace *as;
>      MemoryRegion *memory;
> diff --git a/system/physmem.c b/system/physmem.c
> index 342b7a8fd4..146f17826a 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -763,6 +763,7 @@ 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];
> @@ -776,6 +777,34 @@ void cpu_address_space_init(CPUState *cpu, int asidx,
>      }
>  }
>  
> +void cpu_address_space_destroy(CPUState *cpu, int asidx)
> +{
> +    CPUAddressSpace *cpuas;
> +
> +    assert(cpu->cpu_ases);
> +    assert(asidx >= 0 && asidx < cpu->num_ases);
> +    /* KVM cannot currently support multiple address spaces. */
> +    assert(asidx == 0 || !kvm_enabled());
> +
> +    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 (asidx == 0) {
> +        /* reset the convenience alias for address space 0 */
> +        cpu->as = NULL;
> +    }
> +
> +    if (--cpu->cpu_ases_count == 0) {
> +        g_free(cpu->cpu_ases);
> +        cpu->cpu_ases = NULL;
> +    }
> +}
> +
>  AddressSpace *cpu_get_address_space(CPUState *cpu, int asidx)
>  {
>      /* Return the AddressSpace corresponding to the specified index */