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Date: Thu, 10 Oct 2013 08:30:49 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually
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To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: qemu-devel@nongnu.org

Il 09/10/2013 23:26, Paolo Bonzini ha scritto:
> Il 09/10/2013 21:41, Marcelo Tosatti ha scritto:
>>>> How was that tested?  For BUS_MCEERR_AO it can work, but BUS_MCEERR_AR
>>>> calls force_sig_info which does this:
>>>>
>>>>         ignored = action->sa.sa_handler == SIG_IGN;
>>>>         blocked = sigismember(&t->blocked, sig);
>>>>         if (blocked || ignored) {
>>>>                 action->sa.sa_handler = SIG_DFL;
>>>>                 if (blocked) {
>>>>                         sigdelset(&t->blocked, sig);
>>>>                         recalc_sigpending_and_wake(t);
>>>>                 }
>>>>         
>>>>         if (action->sa.sa_handler == SIG_DFL)
>>>>                 t->signal->flags &= ~SIGNAL_UNKILLABLE;
>>>>
>>>> and kills the process (because that's the default action of SIG_DFL).
>> For vcpu context its not blocked?
> 
> It causes KVM to exit back to userspace, but as soon as KVM exits it
> should be blocked.

... but it's been queued and this bypasses the checks in force_sig_info.
 So in guest mode it is accepted, in QEMU mode it causes a SIGBUS.

Paolo