On 30/11/20 23:42, David Woodhouse wrote:
Yes, good point. Xen*does* allow one hypercall (HVMOP_guest_request_vm_event) from !CPL0 so I don't think I can get away with allowing only CPL0 like kvm_hv_hypercall() does. So unless I'm going to do that filtering in kernel (ick) I think we do need to capture and pass up the CPL, as you say. Which means it doesn't fit in the existing kvm_run->hypercall structure unless I'm prepared to rename/abuse the ->hypercall.pad for it. I'll just use Joao's version of the hypercall support, and add cpl to struct kvm_xen_exit.hcall. Userspace can inject the UD# where appropriate.
Or you can use sync regs perhaps. For your specific use I don't expect many exits to userspace other than Xen hypercalls, so it should be okay to always run with KVM_SYNC_X86_REGS|KVM_SYNC_X86_SREGS in kvm_run->kvm_valid_regs.
Paolo
