[Qemu-devel] Re: [PATCH v2 13/24] kvm: Set up signal mask also for !CONFIG_IOTHREAD

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-02-28 16:55, Avi Kivity wrote:
> On 02/01/2011 11:15 PM, Jan Kiszka wrote:
>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>
>> Block SIG_IPI, unblock it during KVM_RUN, just like in io-thread mode.
>> It's unused so far, but this infrastructure will be required for
>> self-IPIs and to process SIGBUS plus, in KVM mode, SIGIO and SIGALRM. As
>> Windows doesn't support signal services, we need to provide a stub for
>> the init function.
>>
> 
> This patch breaks qemu-kvm after merging.  The symptoms are that Windows
> XP x64 does not respond when netcat connects to some server in it, via
> -net user,hostfwd.  The vcpu thread loops indefinitely on KVM_EXIT_INTR,
> which is consistent with signals being messed up.
> 
> I verified that 981085dd465c1 merged with ff48eb5fe79ad works,
> while 981085dd465c1 merged with ff48eb5fe79ad^ fails.
> 
> 
>> diff --git a/cpus.c b/cpus.c
>> index 42717ba..a33e470 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -231,11 +231,9 @@ fail:
>>       return err;
>>   }
>>
>> -#ifdef CONFIG_IOTHREAD
>>   static void dummy_signal(int sig)
>>   {
>>   }
>> -#endif
>>
>>   #else /* _WIN32 */
>>
>> @@ -267,6 +265,32 @@ static void qemu_event_increment(void)
>>   #endif /* _WIN32 */
>>
>>   #ifndef CONFIG_IOTHREAD
>> +static void qemu_kvm_init_cpu_signals(CPUState *env)
>> +{
>> +#ifndef _WIN32
>> +    int r;
>> +    sigset_t set;
>> +    struct sigaction sigact;
>> +
>> +    memset(&sigact, 0, sizeof(sigact));
>> +    sigact.sa_handler = dummy_signal;
>> +    sigaction(SIG_IPI,&sigact, NULL);
>> +
>> +    sigemptyset(&set);
>> +    sigaddset(&set, SIG_IPI);
>> +    pthread_sigmask(SIG_BLOCK,&set, NULL);
>> +
>> +    pthread_sigmask(SIG_BLOCK, NULL,&set);
>> +    sigdelset(&set, SIG_IPI);
>> +    sigdelset(&set, SIGBUS);
>> +    r = kvm_set_signal_mask(env,&set);
>> +    if (r) {
>> +        fprintf(stderr, "kvm_set_signal_mask: %s\n", strerror(-r));
>> +        exit(1);
>> +    }
>> +#endif
>> +}
>> +
>>   int qemu_init_main_loop(void)
>>   {
>>       cpu_set_debug_excp_handler(cpu_debug_handler);
>> @@ -292,6 +316,7 @@ void qemu_init_vcpu(void *_env)
>>               fprintf(stderr, "kvm_init_vcpu failed: %s\n",
>> strerror(-r));
>>               exit(1);
>>           }
>> +        qemu_kvm_init_cpu_signals(env);

Just comment that out as long as qemu-kvm is (mis-)using !IOTHREAD mode.
I thought it would run before setup_kernel_sigmask, but it's the other
way around, and then the wrong non-iothread signal setup is applied.

Jan

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