[Qemu-devel] Re: [PATCH v3] introduce on_vcpu

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

Glauber Costa wrote:
> on_vcpu is a qemu-kvm function that will make sure that a specific
> piece of code will run on a requested cpu. We don't need that because
> we're restricted to -smp 1 right now, but those days are likely to end soon.
> 
> So for the benefit of having qemu-kvm share more code with us, I'm
> introducing our own version of on_vcpu(). Right now, we either run
> a function on the current cpu, or abort the execution, because it would
> mean something is seriously wrong.
> 
> As an example code, I "ported" kvm_update_guest_debug to use it,
> with some slight differences from qemu-kvm.
> 
> This is probably 0.12 material
> 
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> CC: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  kvm-all.c |   35 +++++++++++++++++++++++++++++------
>  1 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 61194b8..07a1cdb 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -155,6 +155,15 @@ static void kvm_reset_vcpu(void *opaque)
>      }
>  }
>  
> +static void on_vcpu(CPUState *env, void (*func)(void *data), void *data)
> +{
> +    if (env == cpu_single_env) {
> +        func(data);
> +        return;
> +    }
> +    abort();

Sorry, missed this before it went in: This abort fires already now when
kvm_update_guest_debug is invoked by the gdbstub (where cpu_single_env
is 0). This completely breaks guest debugging int kvm mode.

Moreover, if you enable I/O thread support, you already have a need for
true on_vcpu, don't you? Or is locking around the I/O thread still
broken in kvm mode? Anyway, please fix.

Thanks,
Jan

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