On Tue, 12 Mar 2024 at 02:02, Salil Mehta <salil.me...@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.me...@huawei.com>
> Tested-by: Vishnu Pajjuri <vis...@os.amperecomputing.com>
> Reviewed-by: Gavin Shan <gs...@redhat.com>
> Tested-by: Xianglai Li <lixiang...@loongson.cn>
> Tested-by: Miguel Luis <miguel.l...@oracle.com>
> Reviewed-by: Shaoqin Huang <shahu...@redhat.com>
> diff --git a/system/physmem.c b/system/physmem.c
> index 6e9ed97597..61b32ac4f2 100644
> --- a/system/physmem.c
> +++ b/system/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 +775,34 @@ 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;
> + }
> +}
When do we need to destroy a single address space in this way
that means we need to keep a count of how many ASes the CPU
currently has? The commit message talks about the case when we
unrealize the whole CPU object, but in that situation you can
just throw away all the ASes at once (eg by calling some
cpu_destroy_address_spaces() function from cpu_common_unrealizefn()).
Also, if we're leaking stuff here by failing to destroy it,
is that a problem for existing CPU types like x86 that we
can already hotplug?
thanks
-- PMM
