[PATCH v1 3/3] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

[Jon Doron <arilou@gmail.com>]

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 <arilou@gmail.com>
---
 arch/x86/include/asm/hyperv-tlfs.h |  5 +++++
 arch/x86/kvm/hyperv.c              | 11 +++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 8efdf974c23f..4fa6bf3732a6 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -283,6 +283,8 @@
 #define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
 #define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
 
+#define HV_X64_SYNDBG_OPTION_USE_HCALLS		BIT(2)
+
 /* Hyper-V guest crash notification MSR's */
 #define HV_X64_MSR_CRASH_P0			0x40000100
 #define HV_X64_MSR_CRASH_P1			0x40000101
@@ -392,6 +394,9 @@ struct hv_tsc_emulation_status {
 #define HVCALL_SEND_IPI_EX			0x0015
 #define HVCALL_POST_MESSAGE			0x005c
 #define HVCALL_SIGNAL_EVENT			0x005d
+#define HVCALL_POST_DEBUG_DATA			0x0069
+#define HVCALL_RETRIEVE_DEBUG_DATA		0x006a
+#define HVCALL_RESET_DEBUG_SESSION		0x006b
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
 
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 7ec962d433af..593e0f3f4dba 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1794,6 +1794,17 @@ 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:
+	case HVCALL_RESET_DEBUG_SESSION:
+		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;
-- 
2.24.1