Re: [qemu-s390x] [PATCH v1 for-2.11 2/3] s390x/tcg: fix DIAG 308 with > 1 VCPU (single threaded TCG)

[Christian Borntraeger]

Please change the subject. In busy times I tend to ignore tcg patches.
This code is clearly kvm and tcg.
So what about "s390x/diag:" as prefix?

On 11/16/2017 06:05 PM, David Hildenbrand wrote:
> Currently, single threaded TCG with > 1 VCPU gets stuck during IPL, when
> the bios tries to switch to the loaded kernel via DIAG 308.
> 
> pause_all_vcpus()/resume_all_vcpus() should not be called from a VCPU.
> 
> And there is also no need for it. run_on_cpu() will make sure that the
> CPUs exit KVM/TCG, where they get stopped. Once stopped, they will no
> longer run.
> 
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  target/s390x/diag.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/target/s390x/diag.c b/target/s390x/diag.c
> index dbbb9e886f..52bc348808 100644
> --- a/target/s390x/diag.c
> +++ b/target/s390x/diag.c
> @@ -27,7 +27,6 @@ static int modified_clear_reset(S390CPU *cpu)
>      S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
>      CPUState *t;
> 
> -    pause_all_vcpus();


I did this to prevent a "still running CPU to restart an already stopped one".
Are we sure that this can not happen?


>      cpu_synchronize_all_states();
>      CPU_FOREACH(t) {
>          run_on_cpu(t, s390_do_cpu_full_reset, RUN_ON_CPU_NULL);
> @@ -37,7 +36,6 @@ static int modified_clear_reset(S390CPU *cpu)
>      s390_crypto_reset();
>      scc->load_normal(CPU(cpu));
>      cpu_synchronize_all_post_reset();
> -    resume_all_vcpus();
>      return 0;
>  }
> 
> @@ -53,7 +51,6 @@ static int load_normal_reset(S390CPU *cpu)
>      S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
>      CPUState *t;
> 
> -    pause_all_vcpus();
>      cpu_synchronize_all_states();
>      CPU_FOREACH(t) {
>          run_on_cpu(t, s390_do_cpu_reset, RUN_ON_CPU_NULL);
> @@ -63,7 +60,6 @@ static int load_normal_reset(S390CPU *cpu)
>      scc->initial_cpu_reset(CPU(cpu));
>      scc->load_normal(CPU(cpu));
>      cpu_synchronize_all_post_reset();
> -    resume_all_vcpus();
>      return 0;
>  }
>