Le dimanche 10 août 2008 à 11:36 +0300, Avi Kivity a écrit :
> Laurent Vivier wrote:
> > When "halt" is emulated, skip_emulated_instruction() is called and
> > interruptibility state is cleared.
> > But when halt is emulated in real mode, skip_emulated_instruction() is not
> > called and the interruptiblity state is not cleared.
> >
> > The following code, from gPXE, never exits from loop because interrupts are
> > not delivered to increase %fs:(0x6c):
> >
> > movl %fs:(0x6c), %eax
> > 1: pushf
> > sti
> > hlt
> > popf
> > cmpl %fs:(0x6c), %eax
> > je 1b
> >
> > This patch clears the interruptibility state when halt is emulated in real
> > mode.
> >
> > Signed-off-by: Laurent Vivier <[EMAIL PROTECTED]>
> > ---
> > arch/x86/kvm/vmx.c | 10 ++++++++++
> > 1 files changed, 10 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index c4510fe..82c4324 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -2329,7 +2329,17 @@ static int handle_exception(struct kvm_vcpu *vcpu,
> > struct kvm_run *kvm_run)
> > handle_rmode_exception(vcpu, intr_info & INTR_INFO_VECTOR_MASK,
> > error_code)) {
> > if (vcpu->arch.halt_request) {
> > + u32 interruptibility;
> > vcpu->arch.halt_request = 0;
> > + /*
> > + * We emulated an instruction, so temporary interrupt
> > blocking
> > + * should be removed, if set.
> > + */
> > + interruptibility =
> > vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
> > + if (interruptibility & 3)
> > + vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
> > + interruptibility & ~3);
> > + vcpu->arch.interrupt_window_open = 1;
> > return kvm_emulate_halt(vcpu);
> > }
> > return 1;
> >
>
>
> Shouldn't interruptibility state be cleared if *any* instruction is
> emulated?
>
> (of course, an emulated instruction may update interruptibility state
> itself, say sti).
I don't know what to do with that...
I think emulated instructions already clear interruptibility state via
skip_emulated_instruction().
The case of kvm_emulate_halt() and real mode is a special case.
Laurent
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