Re: [PATCH] KVM: x86: Rework INIT and SIPI handling

[Gleb Natapov <gleb@redhat.com>]

On Wed, Mar 13, 2013 at 12:16:13PM +0100, Jan Kiszka wrote:
> >> @@ -1199,11 +1199,8 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu)
> >>
> >>       init_vmcb(svm);
> >>
> >> -     if (!kvm_vcpu_is_bsp(vcpu)) {
> >> +     if (!kvm_vcpu_is_bsp(vcpu))
> >>               kvm_rip_write(vcpu, 0);
> > Table 9-1 in SDM says that after INIT reset RIP is 0xfff0. Not
> > mentioning AP or BSP. We should drop any mentioning of kvm_vcpu_is_bsp()
> > in vmx and svm reset code and thing should just work.
> 
> SDM says that APs start up at 0x000VV000 (with VV == SIPI vector) - this
> implies RIP is 0. I suppose no SMP guest would boot if we change this.
> 
Yes, correct. Setting RIP to 0 should be moved to SIPI handling.

> > 
> >> -             svm->vmcb->save.cs.base = svm->vcpu.arch.sipi_vector << 12;
> >> -             svm->vmcb->save.cs.selector = svm->vcpu.arch.sipi_vector << 8;
> >> -     }
> >>
> >>       kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
> >>       kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> >> index f17cd2a..5b862ed 100644
> >> --- a/arch/x86/kvm/vmx.c
> >> +++ b/arch/x86/kvm/vmx.c
> >> @@ -4121,10 +4121,6 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
> >>       seg_setup(VCPU_SREG_CS);
> >>       if (kvm_vcpu_is_bsp(&vmx->vcpu))
> >>               vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
> >> -     else {
> >> -             vmcs_write16(GUEST_CS_SELECTOR, vmx->vcpu.arch.sipi_vector << 8);
> >> -             vmcs_writel(GUEST_CS_BASE, vmx->vcpu.arch.sipi_vector << 12);
> >> -     }
> >>
> >>       seg_setup(VCPU_SREG_DS);
> >>       seg_setup(VCPU_SREG_ES);
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index b891ac3..37c0807 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -162,8 +162,6 @@ u64 __read_mostly host_xcr0;
> >>
> >>  static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);
> >>
> >> -static void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
> >> -
> >>  static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
> >>  {
> >>       int i;
> >> @@ -2823,10 +2821,9 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
> >>       events->nmi.masked = kvm_x86_ops->get_nmi_mask(vcpu);
> >>       events->nmi.pad = 0;
> >>
> >> -     events->sipi_vector = vcpu->arch.sipi_vector;
> >> +     events->sipi_vector = 0; /* never valid when reporting to user space */
> >>
> >>       events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
> >> -                      | KVM_VCPUEVENT_VALID_SIPI_VECTOR
> >>                        | KVM_VCPUEVENT_VALID_SHADOW);
> >>       memset(&events->reserved, 0, sizeof(events->reserved));
> >>  }
> >> @@ -2857,8 +2854,9 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
> >>               vcpu->arch.nmi_pending = events->nmi.pending;
> >>       kvm_x86_ops->set_nmi_mask(vcpu, events->nmi.masked);
> >>
> >> -     if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR)
> >> -             vcpu->arch.sipi_vector = events->sipi_vector;
> >> +     if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR &&
> >> +         kvm_vcpu_has_lapic(vcpu))
> >> +             vcpu->arch.apic->sipi_vector = events->sipi_vector;
> > This looks out of place in this patch. Why is it needed?
> 
> It is required as long as we support MP_STATE_SIPI_RECEIVED as input
> from user space.
What problem are fixing with adding kvm_vcpu_has_lapic() here?

--
			Gleb.