Re: [PATCH] qemu-kvm: fix guest resetting

[Marcelo Tosatti <mtosatti@redhat.com>]

Hi Jan,

On Thu, May 08, 2008 at 10:29:32AM +0200, Jan Kiszka wrote:
> Resetting guests used to be racy, deadlock-prone, or simply broken (for
> SMP). This patch fixes the issues - at least for me on x86 (tested on
> Intel SMP host, UP and SMP guest, in-kernel und user space irqchip,
> guest- and monitor-issued resets). Note that ia64 and powerpc may need
> to look into the SMP thing as well (=>kvm_arch_cpu_reset).
> 
> At this chance, the patch also cleans up some unneeded reset fragments.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
> @@ -317,11 +317,18 @@ void qemu_kvm_system_reset_request(void)
>  {
>      int i;
>  
> +    pause_all_threads();
> +
> +    qemu_system_reset();
> +
> +    for (i = 0; i < smp_cpus; ++i)
> +	kvm_arch_cpu_reset(vcpu_info[i].env);
> +
>      for (i = 0; i < smp_cpus; ++i) {
> -	vcpu_info[i].reload_regs = 1;
> +	vcpu_info[i].stop = 0;
> +	vcpu_info[i].stopped = 0;
>  	pthread_kill(vcpu_info[i].thread, SIG_IPI);
>      }
> -    qemu_system_reset();

Why don't you signal the IO thread to pause all vcpu's and place their
registers and "run state" in the proper condition if the reset request
comes from the guest? It should simplify things a lot (and avoid any
changes to vl.c).

After signalling the vcpu should stop instead of returning to guest
mode.


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