On Tue, Feb 16, 2010 at 10:16:12AM +0100, Jan Kiszka wrote: > Found while browsing Xen code: While we assume that the STI interrupt > shadow also inplies virtual NMI blocking, some processors may have a > different opinion (SDM 3: 22.3). To avoid misunderstandings that would > cause endless VM entry attempts, translate STI into MOV SS blocking when > requesting the NMI window. > Why not just remove "block by STI" check in vmx_nmi_allowed()? IIRC this is documented that on some CPUs STI does not block NMI.
> Signed-off-by: Jan Kiszka <[email protected]> > --- > > arch/x86/kvm/vmx.c | 15 +++++++++++++++ > 1 files changed, 15 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 14873b9..474f720 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -2614,12 +2614,27 @@ static void enable_irq_window(struct kvm_vcpu *vcpu) > static void enable_nmi_window(struct kvm_vcpu *vcpu) > { > u32 cpu_based_vm_exec_control; > + u32 interruptibility; > > if (!cpu_has_virtual_nmis()) { > enable_irq_window(vcpu); > return; > } > > + /* > + * SDM 3: 22.3 (June 2009) > + * "A logical processor may also prevent such a VM exit [NMI-window > + * exit] if there is blocking of events by STI." > + * So better convert STI blocking into MOV SS to avoid premature VM > + * exits that would end up in an endless loop. > + */ > + interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO); > + if (interruptibility & GUEST_INTR_STATE_STI) { > + interruptibility &= ~GUEST_INTR_STATE_STI; > + interruptibility |= GUEST_INTR_STATE_MOV_SS; > + vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, interruptibility); > + } > + > cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); > cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_NMI_PENDING; > vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control); -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
