[v8,5/5] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

Commit Message

Jon Doron March 19, 2020, 6:38 a.m. UTC

There is another mode for the synthetic debugger which uses hypercalls
to send/recv network data instead of the MSR interface.

This interface is much slower and less recommended since you might get
a lot of VMExits while KDVM polling for new packets to recv, rather
than simply checking the pending page to see if there is data avialble
and then request.

Signed-off-by: Jon Doron <[e-mail]>
---
 arch/x86/kvm/hyperv.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

Patch

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 64f267f10049..0c3d2224dfad 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1829,6 +1829,34 @@  int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		}
 		ret = kvm_hv_send_ipi(vcpu, ingpa, outgpa, true, false);
 		break;
+	case HVCALL_POST_DEBUG_DATA:
+	case HVCALL_RETRIEVE_DEBUG_DATA:
+		if (unlikely(fast)) {
+			ret = HV_STATUS_INVALID_PARAMETER;
+			break;
+		}
+		fallthrough;
+	case HVCALL_RESET_DEBUG_SESSION: {
+		struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+
+		if (!syndbg->active) {
+			ret = HV_STATUS_INVALID_HYPERCALL_CODE;
+			break;
+		}
+
+		if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
+			ret = HV_STATUS_OPERATION_DENIED;
+			break;
+		}
+		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;
+	}
 	default:
 		ret = HV_STATUS_INVALID_HYPERCALL_CODE;
 		break;