Hi Alex,
Alex Bennée writes:
> Pranith Kumar <bobby.pr...@gmail.com> writes:
>
>> In mttcg, calling pause_all_vcpus() during execution from the
>> generated TBs causes a deadlock if some vCPU is waiting for exclusive
>> execution in start_exclusive(). Fix this by using the aync_safe_*
>> framework instead of pausing vcpus for patching instructions.
>>
<...>
>> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
>> index 82a4955..11b0d49 100644
>> --- a/hw/i386/kvmvapic.c
>>
>> - resume_all_vcpus();
>> + g_free(info);
>> +}
>> +
>> +static void patch_instruction(VAPICROMState *s, X86CPU *cpu, target_ulong
>> ip)
>> +{
>> + CPUState *cs = CPU(cpu);
>> + VAPICHandlers *handlers;
>> + struct PatchInfo *info;
>> +
>> + if (smp_cpus == 1) {
>> + handlers = &s->rom_state.up;
>> + } else {
>> + handlers = &s->rom_state.mp;
>> + }
>> +
>> + info = g_new(struct PatchInfo, 1);
>> + info->handler = handlers;
>> + info->ip = ip;
>>
>> if (!kvm_enabled()) {
>> - /* Both tb_lock and iothread_mutex will be reset when
>> - * longjmps back into the cpu_exec loop. */
>> - tb_lock();
>> - tb_gen_code(cs, current_pc, current_cs_base, current_flags, 1);
>> - cpu_loop_exit_noexc(cs);
>> + const run_on_cpu_func fn = do_patch_instruction;
>> +
>> + async_safe_run_on_cpu(cs, fn, RUN_ON_CPU_HOST_PTR(info));
>> + cs->exception_index = EXCP_INTERRUPT;
>> + cpu_loop_exit(cs);
>> }
>> +
>> + pause_all_vcpus();
>> +
>> + do_patch_instruction(cs, RUN_ON_CPU_HOST_PTR(info));
>> +
>> + resume_all_vcpus();
>> + g_free(info);
>
> I don't know if there is any benefit scheduling this as async work for
> KVM but I'll leave that up to Paolo to decide. From a TCG point of view
> I think its good:
>
We are scheduling this as async work only for non-KVM cases. For KVM, we use
go to the pause/resume path above and patch it there itself.
Thanks,
--
Pranith
