Re: KVM: x86: do not execute halted vcpus (resend)

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Sep 10, 2008 at 09:42:05PM +0300, Avi Kivity wrote:
> Marcelo Tosatti wrote:
> >> Actually it does reproduce.  If you reboot twice, the second reboot will  
> >> hang during reset (with cs:ip = f000:fff0).  Plain Windows XP.
> >>     
> >
> > OK, easily reproducible by adding a sleep at the start of
> > qemu_kvm_system_reset.
> >
> > The problem is that the vcpu HLT's between the KBD ioport write and the
> > actual system reset by the IO thread. By then time there will be no
> > event that takes it out of STATE_HALTED.
> >
> > The following fixes it, however older userspace will remain borked.
> > Alternative is to special case f000:fff0 in-kernel. What is preferred?
> >
> >   
> 
> Special-case the kvm_set_sregs ioctl with cs:eip f000:fff0 (and cr0.pe=0
> for good measure).

KVM: x86: unhalt vcpu0 on reset

Since "KVM: x86: do not execute halted vcpus", HLT by vcpu0 before system
reset by the IO thread will hang the guest.

Mark vcpu as runnable in such case.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


Index: kvm.tip/arch/x86/kvm/x86.c
===================================================================
--- kvm.tip.orig/arch/x86/kvm/x86.c
+++ kvm.tip/arch/x86/kvm/x86.c
@@ -3959,6 +3959,11 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct
 	kvm_set_segment(vcpu, &sregs->tr, VCPU_SREG_TR);
 	kvm_set_segment(vcpu, &sregs->ldt, VCPU_SREG_LDTR);
 
+	if (vcpu->vcpu_id == 0 && kvm_rip_read(vcpu) == 0xfff0 &&
+	    sregs->cs.selector == 0xf000 && sregs->cs.base == 0xffff0000 &&
+	    !(vcpu->arch.cr0 & X86_CR0_PE))
+		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+
 	vcpu_put(vcpu);
 
 	return 0;