On Tue, Mar 29, 2016 at 11:34:56AM +0200, Paolo Bonzini wrote: > If SynIC is disabled, there is nothing that userspace can do to > handle these exits; on the other hand, userspace probably will > not know about KVM_EXIT_HYPERV_HCALL and complain about it or > even exit. Just prevent anything bad from happening by handling > the hypercall in KVM and returning an "invalid hypercall" code.
I wonder if this has been encountered in real life or just found by code inspection? > Fixes: 83326e43f27e9a8a501427a0060f8af519a39bb2 > Cc: Andrey Smetanin <[email protected]> > Signed-off-by: Paolo Bonzini <[email protected]> > --- > arch/x86/kvm/hyperv.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > index b960d9ea171f..9e2becd20a59 100644 > --- a/arch/x86/kvm/hyperv.c > +++ b/arch/x86/kvm/hyperv.c > @@ -1237,14 +1237,17 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) > break; > case HVCALL_POST_MESSAGE: > case HVCALL_SIGNAL_EVENT: > - vcpu->run->exit_reason = KVM_EXIT_HYPERV; > - vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL; > - vcpu->run->hyperv.u.hcall.input = param; > - vcpu->run->hyperv.u.hcall.params[0] = ingpa; > - vcpu->run->hyperv.u.hcall.params[1] = outgpa; > - vcpu->arch.complete_userspace_io = > + if (vcpu_to_synic(vcpu)->active) { > + vcpu->run->exit_reason = KVM_EXIT_HYPERV; > + vcpu->run->hyperv.type = KVM_EXIT_HYPERV_HCALL; > + vcpu->run->hyperv.u.hcall.input = param; > + vcpu->run->hyperv.u.hcall.params[0] = ingpa; > + vcpu->run->hyperv.u.hcall.params[1] = outgpa; > + vcpu->arch.complete_userspace_io = > kvm_hv_hypercall_complete_userspace; > - return 0; > + return 0; > + } > + /* fall through */ I'd rather put it the other way around, with explicit error path and a comment: /* don't bother userspace if it has no way to handle it */ if (!vcpu_to_synic(vcpu)->active) { res = HV_STATUS_INVALID_HYPERCALL_CODE; break; } but that's just nitpicking, so Reviewed-by: Roman Kagan <[email protected]> [ Andrey has left the company so I'm not sure he even receives the messages sent to this address ] Thanks, Roman.
