[PATCH v2 0/4] x86/kvm/hyper-v: add support for synthetic debugger

[PATCH v2 0/4] x86/kvm/hyper-v: add support for synthetic debugger

[Jon Doron]

Add support for the synthetic debugger interface of hyper-v, the
synthetic debugger has 2 modes.
1. Use a set of MSRs to send/recv information
2. Use hypercalls

The first mode is based the following MSRs:
1. Control/Status MSRs which either asks for a send/recv .
2. Send/Recv MSRs each holds GPA where the send/recv buffers are.
3. Pending MSR, holds a GPA to a PAGE that simply has a boolean that
   indicates if there is data pending to issue a recv VMEXIT.

In the first patch the first mode is being implemented in the sense that
it simply exits to user-space when a control MSR is being written and
when the pending MSR is being set, then it's up-to userspace to
implement the rest of the logic of sending/recving.

In the second mode instead of using MSRs KNet will simply issue
Hypercalls with the information to send/recv, in this mode the data
being transferred is UDP encapsulated, unlike in the previous mode in
which you get just the data to send.

The new hypercalls will exit to userspace which will be incharge of
re-encapsulating if needed the UDP packets to be sent.

There is an issue though in which KDNet does not respect the hypercall
page and simply issues vmcall/vmmcall instructions depending on the cpu
type expecting them to be handled as it a real hypercall was issued.

Jon Doron (4):
  x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit
  x86/kvm/hyper-v: Add support for synthetic debugger capability
  x86/kvm/hyper-v: enable hypercalls regardless of hypercall page
  x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

 arch/x86/include/asm/hyperv-tlfs.h |  21 +++++
 arch/x86/include/asm/kvm_host.h    |  13 +++
 arch/x86/kvm/hyperv.c              | 136 ++++++++++++++++++++++++++++-
 arch/x86/kvm/hyperv.h              |   5 ++
 arch/x86/kvm/trace.h               |  25 ++++++
 arch/x86/kvm/x86.c                 |   9 ++
 include/uapi/linux/kvm.h           |  11 +++
 7 files changed, 218 insertions(+), 2 deletions(-)

-- 
2.24.1

[PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Jon Doron]

Signed-off-by: Jon Doron <arilou@gmail.com>
---
 include/uapi/linux/kvm.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4b95f9a31a2f..9b4d449f4d20 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -200,6 +200,7 @@ struct kvm_hyperv_exit {
 			__u64 input;
 			__u64 result;
 			__u64 params[2];
+			__u32 pad;
 		} hcall;
 	} u;
 };
-- 
2.24.1

[PATCH v2 2/4] x86/kvm/hyper-v: Add support for synthetic debugger capability

[Jon Doron]

Add support for Hyper-V synthetic debugger (syndbg) interface.
The syndbg interface is using MSRs to emulate a way to send/recv packets
data.

The debug transport dll (kdvm/kdnet) will identify if Hyper-V is enabled
and if it supports the synthetic debugger interface it will attempt to
use it, instead of trying to initialize a network adapter.

Signed-off-by: Jon Doron <arilou@gmail.com>
---
 arch/x86/include/asm/hyperv-tlfs.h |  16 ++++
 arch/x86/include/asm/kvm_host.h    |  13 ++++
 arch/x86/kvm/hyperv.c              | 114 ++++++++++++++++++++++++++++-
 arch/x86/kvm/hyperv.h              |   5 ++
 arch/x86/kvm/trace.h               |  25 +++++++
 arch/x86/kvm/x86.c                 |   9 +++
 include/uapi/linux/kvm.h           |  10 +++
 7 files changed, 191 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 92abc1e42bfc..8efdf974c23f 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -33,6 +33,9 @@
 #define HYPERV_CPUID_ENLIGHTMENT_INFO		0x40000004
 #define HYPERV_CPUID_IMPLEMENT_LIMITS		0x40000005
 #define HYPERV_CPUID_NESTED_FEATURES		0x4000000A
+#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
+#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
+#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
 
 #define HYPERV_HYPERVISOR_PRESENT_BIT		0x80000000
 #define HYPERV_CPUID_MIN			0x40000005
@@ -131,6 +134,8 @@
 #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE		BIT(8)
 /* Crash MSR available */
 #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE		BIT(10)
+/* Support for debug MSRs available */
+#define HV_FEATURE_DEBUG_MSRS_AVAILABLE			BIT(11)
 /* stimer Direct Mode is available */
 #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
 
@@ -194,6 +199,9 @@
 #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
 #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
 
+/* Hyper-V synthetic debugger platform capabilities */
+#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
+
 /* Hyper-V specific model specific registers (MSRs) */
 
 /* MSR used to identify the guest OS. */
@@ -267,6 +275,14 @@
 /* Hyper-V guest idle MSR */
 #define HV_X64_MSR_GUEST_IDLE			0x400000F0
 
+/* Hyper-V Synthetic debug options MSR */
+#define HV_X64_MSR_SYNDBG_CONTROL		0x400000F1
+#define HV_X64_MSR_SYNDBG_STATUS		0x400000F2
+#define HV_X64_MSR_SYNDBG_SEND_BUFFER		0x400000F3
+#define HV_X64_MSR_SYNDBG_RECV_BUFFER		0x400000F4
+#define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
+#define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
+
 /* Hyper-V guest crash notification MSR's */
 #define HV_X64_MSR_CRASH_P0			0x40000100
 #define HV_X64_MSR_CRASH_P1			0x40000101
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 98959e8cd448..f8e58e8866bb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -854,6 +854,18 @@ struct kvm_apic_map {
 	struct kvm_lapic *phys_map[];
 };
 
+/* Hyper-V synthetic debugger (SynDbg)*/
+struct kvm_hv_syndbg {
+	struct {
+		u64 control;
+		u64 status;
+		u64 send_page;
+		u64 recv_page;
+		u64 pending_page;
+	} control;
+	u64 options;
+};
+
 /* Hyper-V emulation context */
 struct kvm_hv {
 	struct mutex hv_lock;
@@ -877,6 +889,7 @@ struct kvm_hv {
 	atomic_t num_mismatched_vp_indexes;
 
 	struct hv_partition_assist_pg *hv_pa_pg;
+	struct kvm_hv_syndbg hv_syndbg;
 };
 
 enum kvm_irqchip_mode {
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index a86fda7a1d03..7cbc4afe9d07 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -266,6 +266,71 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
 	return ret;
 }
 
+static int kvm_hv_syndbg_complete_userspace(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_hv *hv = &kvm->arch.hyperv;
+
+	if (vcpu->run->hyperv.u.syndbg.msr == HV_X64_MSR_SYNDBG_CONTROL)
+		hv->hv_syndbg.control.status =
+			vcpu->run->hyperv.u.syndbg.status;
+	return 1;
+}
+
+static void syndbg_exit(struct kvm_vcpu *vcpu, u32 msr)
+{
+	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+	struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
+
+	hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNDBG;
+	hv_vcpu->exit.u.syndbg.msr = msr;
+	hv_vcpu->exit.u.syndbg.control = syndbg->control.control;
+	hv_vcpu->exit.u.syndbg.send_page = syndbg->control.send_page;
+	hv_vcpu->exit.u.syndbg.recv_page = syndbg->control.recv_page;
+	hv_vcpu->exit.u.syndbg.pending_page = syndbg->control.pending_page;
+	vcpu->arch.complete_userspace_io =
+			kvm_hv_syndbg_complete_userspace;
+
+	kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
+}
+
+static int syndbg_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
+{
+	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+	int ret;
+
+	trace_kvm_hv_syndbg_set_msr(vcpu->vcpu_id,
+				    vcpu_to_hv_vcpu(vcpu)->vp_index, msr, data);
+	ret = 0;
+	switch (msr) {
+	case HV_X64_MSR_SYNDBG_CONTROL:
+		syndbg->control.control = data;
+		syndbg_exit(vcpu, msr);
+		break;
+	case HV_X64_MSR_SYNDBG_STATUS:
+		syndbg->control.status = data;
+		break;
+	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
+		syndbg->control.send_page = data;
+		break;
+	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
+		syndbg->control.recv_page = data;
+		break;
+	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+		syndbg->control.pending_page = data;
+		syndbg_exit(vcpu, msr);
+		break;
+	case HV_X64_MSR_SYNDBG_OPTIONS:
+		syndbg->options = data;
+		break;
+	default:
+		ret = 1;
+		break;
+	}
+
+	return ret;
+}
+
 static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
 			 bool host)
 {
@@ -800,6 +865,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
 	case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
 	case HV_X64_MSR_TSC_EMULATION_CONTROL:
 	case HV_X64_MSR_TSC_EMULATION_STATUS:
+	case HV_X64_MSR_SYNDBG_OPTIONS:
+	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
 		r = true;
 		break;
 	}
@@ -1061,6 +1128,9 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 		if (!host)
 			return 1;
 		break;
+	case HV_X64_MSR_SYNDBG_OPTIONS:
+	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+		return syndbg_set_msr(vcpu, msr, data);
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
 			    msr, data);
@@ -1227,6 +1297,24 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case HV_X64_MSR_TSC_EMULATION_STATUS:
 		data = hv->hv_tsc_emulation_status;
 		break;
+	case HV_X64_MSR_SYNDBG_OPTIONS:
+		data = hv->hv_syndbg.options;
+		break;
+	case HV_X64_MSR_SYNDBG_CONTROL:
+		data = hv->hv_syndbg.control.control;
+		break;
+	case HV_X64_MSR_SYNDBG_STATUS:
+		data = hv->hv_syndbg.control.status;
+		break;
+	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
+		data = hv->hv_syndbg.control.send_page;
+		break;
+	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
+		data = hv->hv_syndbg.control.recv_page;
+		break;
+	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+		data = hv->hv_syndbg.control.pending_page;
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
 		return 1;
@@ -1797,6 +1885,9 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 		{ .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
 		{ .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
 		{ .function = HYPERV_CPUID_NESTED_FEATURES },
+		{ .function = HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS },
+		{ .function = HYPERV_CPUID_SYNDBG_INTERFACE },
+		{ .function = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	},
 	};
 	int i, nent = ARRAY_SIZE(cpuid_entries);
 
@@ -1821,7 +1912,7 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 		case HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS:
 			memcpy(signature, "Linux KVM Hv", 12);
 
-			ent->eax = HYPERV_CPUID_NESTED_FEATURES;
+			ent->eax = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES;
 			ent->ebx = signature[0];
 			ent->ecx = signature[1];
 			ent->edx = signature[2];
@@ -1856,9 +1947,12 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 
 			ent->ebx |= HV_X64_POST_MESSAGES;
 			ent->ebx |= HV_X64_SIGNAL_EVENTS;
+			ent->ebx |= HV_X64_DEBUGGING;
 
 			ent->edx |= HV_FEATURE_FREQUENCY_MSRS_AVAILABLE;
 			ent->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
+			ent->edx |= HV_X64_GUEST_DEBUGGING_AVAILABLE;
+			ent->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
 
 			/*
 			 * Direct Synthetic timers only make sense with in-kernel
@@ -1903,6 +1997,24 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 
 			break;
 
+		case HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS:
+			memcpy(signature, "Linux KVM Hv", 12);
+
+			ent->eax = 0;
+			ent->ebx = signature[0];
+			ent->ecx = signature[1];
+			ent->edx = signature[2];
+			break;
+
+		case HYPERV_CPUID_SYNDBG_INTERFACE:
+			memcpy(signature, "VS#1\0\0\0\0\0\0\0\0", 12);
+			ent->eax = signature[0];
+			break;
+
+		case HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES:
+			ent->eax |= HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
+			break;
+
 		default:
 			break;
 		}
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 757cb578101c..6a86151fac53 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -46,6 +46,11 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
 	return hv_vcpu_to_vcpu(container_of(synic, struct kvm_vcpu_hv, synic));
 }
 
+static inline struct kvm_hv_syndbg *vcpu_to_hv_syndbg(struct kvm_vcpu *vcpu)
+{
+	return &vcpu->kvm->arch.hyperv.hv_syndbg;
+}
+
 int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
 int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
 
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index f194dd058470..5fd600916fd4 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -1515,6 +1515,31 @@ TRACE_EVENT(kvm_nested_vmenter_failed,
 		__print_symbolic(__entry->err, VMX_VMENTER_INSTRUCTION_ERRORS))
 );
 
+/*
+ * Tracepoint for syndbg_set_msr.
+ */
+TRACE_EVENT(kvm_hv_syndbg_set_msr,
+	TP_PROTO(int vcpu_id, u32 vp_index, u32 msr, u64 data),
+	TP_ARGS(vcpu_id, vp_index, msr, data),
+
+	TP_STRUCT__entry(
+		__field(int, vcpu_id)
+		__field(u32, vp_index)
+		__field(u32, msr)
+		__field(u64, data)
+	),
+
+	TP_fast_assign(
+		__entry->vcpu_id = vcpu_id;
+		__entry->vp_index = vp_index;
+		__entry->msr = msr;
+		__entry->data = data;
+	),
+
+	TP_printk("vcpu_id %d vp_index %u msr 0x%x data 0x%llx",
+		  __entry->vcpu_id, __entry->vp_index, __entry->msr,
+		  __entry->data)
+);
 #endif /* _TRACE_KVM_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5de200663f51..619c24bac79e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1214,6 +1214,10 @@ static const u32 emulated_msrs_all[] = {
 	HV_X64_MSR_VP_ASSIST_PAGE,
 	HV_X64_MSR_REENLIGHTENMENT_CONTROL, HV_X64_MSR_TSC_EMULATION_CONTROL,
 	HV_X64_MSR_TSC_EMULATION_STATUS,
+	HV_X64_MSR_SYNDBG_OPTIONS,
+	HV_X64_MSR_SYNDBG_CONTROL, HV_X64_MSR_SYNDBG_STATUS,
+	HV_X64_MSR_SYNDBG_SEND_BUFFER, HV_X64_MSR_SYNDBG_RECV_BUFFER,
+	HV_X64_MSR_SYNDBG_PENDING_BUFFER,
 
 	MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
 	MSR_KVM_PV_EOI_EN,
@@ -2906,6 +2910,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		 */
 		break;
 	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
+	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+	case HV_X64_MSR_SYNDBG_OPTIONS:
 	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
 	case HV_X64_MSR_CRASH_CTL:
 	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
@@ -3151,6 +3157,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = 0x20000000;
 		break;
 	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
+	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+	case HV_X64_MSR_SYNDBG_OPTIONS:
 	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
 	case HV_X64_MSR_CRASH_CTL:
 	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
@@ -3323,6 +3331,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_HYPERV_TLBFLUSH:
 	case KVM_CAP_HYPERV_SEND_IPI:
 	case KVM_CAP_HYPERV_CPUID:
+	case KVM_CAP_HYPERV_DEBUGGING:
 	case KVM_CAP_PCI_SEGMENT:
 	case KVM_CAP_DEBUGREGS:
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 9b4d449f4d20..ca28ea04d1d5 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -188,6 +188,7 @@ struct kvm_s390_cmma_log {
 struct kvm_hyperv_exit {
 #define KVM_EXIT_HYPERV_SYNIC          1
 #define KVM_EXIT_HYPERV_HCALL          2
+#define KVM_EXIT_HYPERV_SYNDBG         3
 	__u32 type;
 	union {
 		struct {
@@ -202,6 +203,14 @@ struct kvm_hyperv_exit {
 			__u64 params[2];
 			__u32 pad;
 		} hcall;
+		struct {
+			__u32 msr;
+			__u64 control;
+			__u64 status;
+			__u64 send_page;
+			__u64 recv_page;
+			__u64 pending_page;
+		} syndbg;
 	} u;
 };
 
@@ -1011,6 +1020,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_ARM_NISV_TO_USER 177
 #define KVM_CAP_ARM_INJECT_EXT_DABT 178
 #define KVM_CAP_S390_VCPU_RESETS 179
+#define KVM_CAP_HYPERV_DEBUGGING 180
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.24.1

[PATCH v2 3/4] x86/kvm/hyper-v: enable hypercalls regardless of hypercall page

[Jon Doron]

Microsoft's kdvm.dll dbgtransport module does not respect the hypercall
page and simply identifies the CPU being used (AMD/Intel) and according
to it simply makes hypercalls with the relevant instruction
(vmmcall/vmcall respectively).

The relevant function in kdvm is KdHvConnectHypervisor which first checks
if the hypercall page has been enabled via HV_X64_MSR_HYPERCALL_ENABLE,
and in case it was not it simply sets the HV_X64_MSR_GUEST_OS_ID to
0x1000101010001 which means:
build_number = 0x0001
service_version = 0x01
minor_version = 0x01
major_version = 0x01
os_id = 0x00 (Undefined)
vendor_id = 1 (Microsoft)
os_type = 0 (A value of 0 indicates a proprietary, closed source OS)

and starts issuing the hypercall without setting the hypercall page.

To resolve this issue simply enable hypercalls also if the guest_os_id
is not 0.

Signed-off-by: Jon Doron <arilou@gmail.com>
---
 arch/x86/kvm/hyperv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 7cbc4afe9d07..d657a312004a 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1618,7 +1618,10 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *current_vcpu, u64 ingpa, u64 outgpa,
 
 bool kvm_hv_hypercall_enabled(struct kvm *kvm)
 {
-	return READ_ONCE(kvm->arch.hyperv.hv_hypercall) & HV_X64_MSR_HYPERCALL_ENABLE;
+	struct kvm_hv *hv = &kvm->arch.hyperv;
+
+	return READ_ONCE(hv->hv_hypercall) & HV_X64_MSR_HYPERCALL_ENABLE ||
+	       READ_ONCE(hv->hv_guest_os_id) != 0;
 }
 
 static void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)
-- 
2.24.1

[PATCH v2 4/4] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

[Jon Doron]

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              | 17 +++++++++++++++++
 2 files changed, 22 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 d657a312004a..52517e11e643 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1800,6 +1800,23 @@ 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: {
+		struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+		if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
+			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
+			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;
-- 
2.24.1

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Paolo Bonzini]

On 05/03/20 15:01, Jon Doron wrote:
> Signed-off-by: Jon Doron <arilou@gmail.com>
> ---
>  include/uapi/linux/kvm.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4b95f9a31a2f..9b4d449f4d20 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -200,6 +200,7 @@ struct kvm_hyperv_exit {
>  			__u64 input;
>  			__u64 result;
>  			__u64 params[2];
> +			__u32 pad;
>  		} hcall;
>  	} u;
>  };
> 

Can you explain the purpose of this patch?

Paolo

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Jon Doron]

Vitaly recommended we will align the struct to 64bit...

On Thu, Mar 5, 2020 at 4:24 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 05/03/20 15:01, Jon Doron wrote:
> > Signed-off-by: Jon Doron <arilou@gmail.com>
> > ---
> >  include/uapi/linux/kvm.h | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 4b95f9a31a2f..9b4d449f4d20 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -200,6 +200,7 @@ struct kvm_hyperv_exit {
> >                       __u64 input;
> >                       __u64 result;
> >                       __u64 params[2];
> > +                     __u32 pad;
> >               } hcall;
> >       } u;
> >  };
> >
>
> Can you explain the purpose of this patch?
>
> Paolo
>

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Paolo Bonzini]

On 05/03/20 15:53, Jon Doron wrote:
> Vitaly recommended we will align the struct to 64bit...

Oh, then I think you actually should add a padding after "__u32 type;"
and "__u32 msr;" if you want to make it explicit.  The patch, as is, is
not aligning anything, hence my confusion.

Thanks,

Paolo

> On Thu, Mar 5, 2020 at 4:24 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>> On 05/03/20 15:01, Jon Doron wrote:
>>> Signed-off-by: Jon Doron <arilou@gmail.com>
>>> ---
>>>  include/uapi/linux/kvm.h | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>>> index 4b95f9a31a2f..9b4d449f4d20 100644
>>> --- a/include/uapi/linux/kvm.h
>>> +++ b/include/uapi/linux/kvm.h
>>> @@ -200,6 +200,7 @@ struct kvm_hyperv_exit {
>>>                       __u64 input;
>>>                       __u64 result;
>>>                       __u64 params[2];
>>> +                     __u32 pad;
>>>               } hcall;
>>>       } u;
>>>  };
>>>
>>
>> Can you explain the purpose of this patch?
>>
>> Paolo
>>
> 

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Jon Doron]

bah you are right sorry :( but if ill do that ill break userspace no?
-- Jon..

On Thu, Mar 5, 2020 at 5:30 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 05/03/20 15:53, Jon Doron wrote:
> > Vitaly recommended we will align the struct to 64bit...
>
> Oh, then I think you actually should add a padding after "__u32 type;"
> and "__u32 msr;" if you want to make it explicit.  The patch, as is, is
> not aligning anything, hence my confusion.
>
> Thanks,
>
> Paolo
>
> > On Thu, Mar 5, 2020 at 4:24 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
> >>
> >> On 05/03/20 15:01, Jon Doron wrote:
> >>> Signed-off-by: Jon Doron <arilou@gmail.com>
> >>> ---
> >>>  include/uapi/linux/kvm.h | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> >>> index 4b95f9a31a2f..9b4d449f4d20 100644
> >>> --- a/include/uapi/linux/kvm.h
> >>> +++ b/include/uapi/linux/kvm.h
> >>> @@ -200,6 +200,7 @@ struct kvm_hyperv_exit {
> >>>                       __u64 input;
> >>>                       __u64 result;
> >>>                       __u64 params[2];
> >>> +                     __u32 pad;
> >>>               } hcall;
> >>>       } u;
> >>>  };
> >>>
> >>
> >> Can you explain the purpose of this patch?
> >>
> >> Paolo
> >>
> >
>

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Paolo Bonzini]

On 05/03/20 16:52, Jon Doron wrote:
> bah you are right sorry :( but if ill do that ill break userspace no?

No, you'd just be making the padding explicit.

Paolo

> 
> On Thu, Mar 5, 2020 at 5:30 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On 05/03/20 15:53, Jon Doron wrote:
>>> Vitaly recommended we will align the struct to 64bit...
>> Oh, then I think you actually should add a padding after "__u32 type;"
>> and "__u32 msr;" if you want to make it explicit.  The patch, as is, is
>> not aligning anything, hence my confusion.

Re: [PATCH v2 1/4] x86/kvm/hyper-v: Align the hcall param for kvm_hyperv_exit

[Jon Doron]

Thanks Vitaly and Paoloo I'll fix the 1st patch and wait for the final
review on the other 3 and submit v3, I'll also look into adding
the proper test for the Hypercall patch to
https://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git, and submit
a separate patch
to that repository.

Thanks,
-- Jon.

On Fri, Mar 6, 2020 at 12:30 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> Paolo Bonzini <pbonzini@redhat.com> writes:
>
> > On 05/03/20 15:53, Jon Doron wrote:
> >> Vitaly recommended we will align the struct to 64bit...
> >
> > Oh, then I think you actually should add a padding after "__u32 type;"
> > and "__u32 msr;" if you want to make it explicit.  The patch, as is, is
> > not aligning anything, hence my confusion.
> >
>
> Right,
>
> the problem I tried to highlight is that without propper padding ABI may
> change, e.g.
>
> #include <stdio.h>
> #include <stdint.h>
> #include <stddef.h>
>
> #define __u32 uint32_t
> #define __u64 uint64_t
>
> struct kvm_hyperv_exit {
>         __u32 type;
>         union {
>                 struct {
>                         __u32 msr;
>                         __u64 control;
>                         __u64 evt_page;
>                         __u64 msg_page;
>                 } synic;
>                 struct {
>                         __u64 input;
>                         __u64 result;
>                         __u64 params[2];
>                 } hcall;
>         } u;
> };
>
> int main() {
>         printf("%d\n", offsetof(struct kvm_hyperv_exit, u.synic.control));
>         printf("%d\n", offsetof(struct kvm_hyperv_exit, u.hcall.input));
>
>         return 0;
> }
>
> $ gcc -m32 1.c -o 1
> $ ./1
> 8
> 4
>
> $ gcc 1.c -o 1
> $ ./1
> 16
> 8
>
> if we add a padding after 'type' and 'msr' we'll get
> $ gcc -m32 1.c -o 1
> $ ./1
> 16
> 8
>
> $ gcc 1.c -o 1
> $ ./1
> 16
> 8
>
> which is much better. Technically, this is an ABI change on 32 bit but
> I'm pretty sure noone cares (famous last words!).
>
> --
> Vitaly
>

Re: [PATCH v2 2/4] x86/kvm/hyper-v: Add support for synthetic debugger capability

[Vitaly Kuznetsov]

Jon Doron <arilou@gmail.com> writes:

> Add support for Hyper-V synthetic debugger (syndbg) interface.
> The syndbg interface is using MSRs to emulate a way to send/recv packets
> data.
>
> The debug transport dll (kdvm/kdnet) will identify if Hyper-V is enabled
> and if it supports the synthetic debugger interface it will attempt to
> use it, instead of trying to initialize a network adapter.
>

I would suggest you split TLFS changes into it's own patch so Hyper-V
folks can ACK (or they can ack the whole patch with KVM changes of
course :-)

> Signed-off-by: Jon Doron <arilou@gmail.com>
> ---
>  arch/x86/include/asm/hyperv-tlfs.h |  16 ++++
>  arch/x86/include/asm/kvm_host.h    |  13 ++++
>  arch/x86/kvm/hyperv.c              | 114 ++++++++++++++++++++++++++++-
>  arch/x86/kvm/hyperv.h              |   5 ++
>  arch/x86/kvm/trace.h               |  25 +++++++
>  arch/x86/kvm/x86.c                 |   9 +++
>  include/uapi/linux/kvm.h           |  10 +++
>  7 files changed, 191 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 92abc1e42bfc..8efdf974c23f 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -33,6 +33,9 @@
>  #define HYPERV_CPUID_ENLIGHTMENT_INFO		0x40000004
>  #define HYPERV_CPUID_IMPLEMENT_LIMITS		0x40000005
>  #define HYPERV_CPUID_NESTED_FEATURES		0x4000000A
> +#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
> +#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
> +#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
>  
>  #define HYPERV_HYPERVISOR_PRESENT_BIT		0x80000000
>  #define HYPERV_CPUID_MIN			0x40000005
> @@ -131,6 +134,8 @@
>  #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE		BIT(8)
>  /* Crash MSR available */
>  #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE		BIT(10)
> +/* Support for debug MSRs available */
> +#define HV_FEATURE_DEBUG_MSRS_AVAILABLE			BIT(11)
>  /* stimer Direct Mode is available */
>  #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
>  
> @@ -194,6 +199,9 @@
>  #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
>  #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
>  
> +/* Hyper-V synthetic debugger platform capabilities */
> +#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
> +

hyperv-tlfs.h is not perfectly structured but still there is some
structure there,
e.g. HV_X64_NESTED_GUEST_MAPPING_FLUSH/HV_X64_NESTED_MSR_BITMAP/... are
said to be HYPERV_CPUID_ENLIGHTMENT_INFO.EAX
bits (see above HV_X64_AS_SWITCH_RECOMMENDED).

To make it clear that HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING doesn't
belong to these bits I'd suggest you add a comment like  

/*
 * Hyper-V synthetic debugger platform capabilities.
 * These are HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits.
 * 
*/

to make it clear.

>  /* Hyper-V specific model specific registers (MSRs) */
>  
>  /* MSR used to identify the guest OS. */
> @@ -267,6 +275,14 @@
>  /* Hyper-V guest idle MSR */
>  #define HV_X64_MSR_GUEST_IDLE			0x400000F0
>  
> +/* Hyper-V Synthetic debug options MSR */
> +#define HV_X64_MSR_SYNDBG_CONTROL		0x400000F1
> +#define HV_X64_MSR_SYNDBG_STATUS		0x400000F2
> +#define HV_X64_MSR_SYNDBG_SEND_BUFFER		0x400000F3
> +#define HV_X64_MSR_SYNDBG_RECV_BUFFER		0x400000F4
> +#define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
> +#define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
> +
>  /* Hyper-V guest crash notification MSR's */
>  #define HV_X64_MSR_CRASH_P0			0x40000100
>  #define HV_X64_MSR_CRASH_P1			0x40000101
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 98959e8cd448..f8e58e8866bb 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -854,6 +854,18 @@ struct kvm_apic_map {
>  	struct kvm_lapic *phys_map[];
>  };
>  
> +/* Hyper-V synthetic debugger (SynDbg)*/
> +struct kvm_hv_syndbg {
> +	struct {
> +		u64 control;
> +		u64 status;
> +		u64 send_page;
> +		u64 recv_page;
> +		u64 pending_page;
> +	} control;
> +	u64 options;
> +};
> +
>  /* Hyper-V emulation context */
>  struct kvm_hv {
>  	struct mutex hv_lock;
> @@ -877,6 +889,7 @@ struct kvm_hv {
>  	atomic_t num_mismatched_vp_indexes;
>  
>  	struct hv_partition_assist_pg *hv_pa_pg;
> +	struct kvm_hv_syndbg hv_syndbg;
>  };
>  
>  enum kvm_irqchip_mode {
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index a86fda7a1d03..7cbc4afe9d07 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -266,6 +266,71 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>  	return ret;
>  }
>  
> +static int kvm_hv_syndbg_complete_userspace(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_hv *hv = &kvm->arch.hyperv;
> +
> +	if (vcpu->run->hyperv.u.syndbg.msr == HV_X64_MSR_SYNDBG_CONTROL)
> +		hv->hv_syndbg.control.status =
> +			vcpu->run->hyperv.u.syndbg.status;
> +	return 1;
> +}
> +
> +static void syndbg_exit(struct kvm_vcpu *vcpu, u32 msr)
> +{
> +	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
> +	struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
> +
> +	hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNDBG;
> +	hv_vcpu->exit.u.syndbg.msr = msr;
> +	hv_vcpu->exit.u.syndbg.control = syndbg->control.control;
> +	hv_vcpu->exit.u.syndbg.send_page = syndbg->control.send_page;
> +	hv_vcpu->exit.u.syndbg.recv_page = syndbg->control.recv_page;
> +	hv_vcpu->exit.u.syndbg.pending_page = syndbg->control.pending_page;
> +	vcpu->arch.complete_userspace_io =
> +			kvm_hv_syndbg_complete_userspace;
> +
> +	kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
> +}
> +
> +static int syndbg_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> +{
> +	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
> +	int ret;
> +
> +	trace_kvm_hv_syndbg_set_msr(vcpu->vcpu_id,
> +				    vcpu_to_hv_vcpu(vcpu)->vp_index, msr, data);
> +	ret = 0;
> +	switch (msr) {
> +	case HV_X64_MSR_SYNDBG_CONTROL:
> +		syndbg->control.control = data;
> +		syndbg_exit(vcpu, msr);
> +		break;
> +	case HV_X64_MSR_SYNDBG_STATUS:
> +		syndbg->control.status = data;
> +		break;
> +	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
> +		syndbg->control.send_page = data;
> +		break;
> +	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
> +		syndbg->control.recv_page = data;
> +		break;
> +	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> +		syndbg->control.pending_page = data;
> +		syndbg_exit(vcpu, msr);
> +		break;
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
> +		syndbg->options = data;
> +		break;
> +	default:
> +		ret = 1;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>  static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
>  			 bool host)
>  {
> @@ -800,6 +865,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
>  	case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
>  	case HV_X64_MSR_TSC_EMULATION_CONTROL:
>  	case HV_X64_MSR_TSC_EMULATION_STATUS:
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>  		r = true;
>  		break;
>  	}
> @@ -1061,6 +1128,9 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
>  		if (!host)
>  			return 1;
>  		break;
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> +		return syndbg_set_msr(vcpu, msr, data);
>  	default:
>  		vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
>  			    msr, data);
> @@ -1227,6 +1297,24 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>  	case HV_X64_MSR_TSC_EMULATION_STATUS:
>  		data = hv->hv_tsc_emulation_status;
>  		break;
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
> +		data = hv->hv_syndbg.options;
> +		break;
> +	case HV_X64_MSR_SYNDBG_CONTROL:
> +		data = hv->hv_syndbg.control.control;
> +		break;
> +	case HV_X64_MSR_SYNDBG_STATUS:
> +		data = hv->hv_syndbg.control.status;
> +		break;
> +	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
> +		data = hv->hv_syndbg.control.send_page;
> +		break;
> +	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
> +		data = hv->hv_syndbg.control.recv_page;
> +		break;
> +	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> +		data = hv->hv_syndbg.control.pending_page;
> +		break;
>  	default:
>  		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
>  		return 1;
> @@ -1797,6 +1885,9 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>  		{ .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
>  		{ .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
>  		{ .function = HYPERV_CPUID_NESTED_FEATURES },
> +		{ .function = HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS },
> +		{ .function = HYPERV_CPUID_SYNDBG_INTERFACE },
> +		{ .function = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	},
>  	};
>  	int i, nent = ARRAY_SIZE(cpuid_entries);
>  
> @@ -1821,7 +1912,7 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>  		case HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS:
>  			memcpy(signature, "Linux KVM Hv", 12);
>  
> -			ent->eax = HYPERV_CPUID_NESTED_FEATURES;
> +			ent->eax = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES;
>  			ent->ebx = signature[0];
>  			ent->ecx = signature[1];
>  			ent->edx = signature[2];
> @@ -1856,9 +1947,12 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>  
>  			ent->ebx |= HV_X64_POST_MESSAGES;
>  			ent->ebx |= HV_X64_SIGNAL_EVENTS;
> +			ent->ebx |= HV_X64_DEBUGGING;
>  
>  			ent->edx |= HV_FEATURE_FREQUENCY_MSRS_AVAILABLE;
>  			ent->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
> +			ent->edx |= HV_X64_GUEST_DEBUGGING_AVAILABLE;
> +			ent->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
>  
>  			/*
>  			 * Direct Synthetic timers only make sense with in-kernel
> @@ -1903,6 +1997,24 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>  
>  			break;
>  
> +		case HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS:
> +			memcpy(signature, "Linux KVM Hv", 12);
> +
> +			ent->eax = 0;
> +			ent->ebx = signature[0];
> +			ent->ecx = signature[1];
> +			ent->edx = signature[2];

or maybe just copy HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS.EBX if it's not
any different?

> +			break;
> +
> +		case HYPERV_CPUID_SYNDBG_INTERFACE:
> +			memcpy(signature, "VS#1\0\0\0\0\0\0\0\0", 12);
> +			ent->eax = signature[0];
> +			break;
> +
> +		case HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES:
> +			ent->eax |= HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
> +			break;
> +
>  		default:
>  			break;
>  		}
> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
> index 757cb578101c..6a86151fac53 100644
> --- a/arch/x86/kvm/hyperv.h
> +++ b/arch/x86/kvm/hyperv.h
> @@ -46,6 +46,11 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
>  	return hv_vcpu_to_vcpu(container_of(synic, struct kvm_vcpu_hv, synic));
>  }
>  
> +static inline struct kvm_hv_syndbg *vcpu_to_hv_syndbg(struct kvm_vcpu *vcpu)
> +{
> +	return &vcpu->kvm->arch.hyperv.hv_syndbg;
> +}
> +
>  int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
>  int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
>  
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index f194dd058470..5fd600916fd4 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -1515,6 +1515,31 @@ TRACE_EVENT(kvm_nested_vmenter_failed,
>  		__print_symbolic(__entry->err, VMX_VMENTER_INSTRUCTION_ERRORS))
>  );
>  
> +/*
> + * Tracepoint for syndbg_set_msr.
> + */
> +TRACE_EVENT(kvm_hv_syndbg_set_msr,
> +	TP_PROTO(int vcpu_id, u32 vp_index, u32 msr, u64 data),
> +	TP_ARGS(vcpu_id, vp_index, msr, data),
> +
> +	TP_STRUCT__entry(
> +		__field(int, vcpu_id)
> +		__field(u32, vp_index)
> +		__field(u32, msr)
> +		__field(u64, data)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->vcpu_id = vcpu_id;
> +		__entry->vp_index = vp_index;
> +		__entry->msr = msr;
> +		__entry->data = data;
> +	),
> +
> +	TP_printk("vcpu_id %d vp_index %u msr 0x%x data 0x%llx",
> +		  __entry->vcpu_id, __entry->vp_index, __entry->msr,
> +		  __entry->data)
> +);

To be consistent, do we also want a kvm_hv_syndbg_get_msr tracepoint?

>  #endif /* _TRACE_KVM_H */
>  
>  #undef TRACE_INCLUDE_PATH
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5de200663f51..619c24bac79e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1214,6 +1214,10 @@ static const u32 emulated_msrs_all[] = {
>  	HV_X64_MSR_VP_ASSIST_PAGE,
>  	HV_X64_MSR_REENLIGHTENMENT_CONTROL, HV_X64_MSR_TSC_EMULATION_CONTROL,
>  	HV_X64_MSR_TSC_EMULATION_STATUS,
> +	HV_X64_MSR_SYNDBG_OPTIONS,
> +	HV_X64_MSR_SYNDBG_CONTROL, HV_X64_MSR_SYNDBG_STATUS,
> +	HV_X64_MSR_SYNDBG_SEND_BUFFER, HV_X64_MSR_SYNDBG_RECV_BUFFER,
> +	HV_X64_MSR_SYNDBG_PENDING_BUFFER,
>  
>  	MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
>  	MSR_KVM_PV_EOI_EN,
> @@ -2906,6 +2910,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		 */
>  		break;
>  	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>  	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
>  	case HV_X64_MSR_CRASH_CTL:
>  	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
> @@ -3151,6 +3157,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		msr_info->data = 0x20000000;
>  		break;
>  	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>  	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
>  	case HV_X64_MSR_CRASH_CTL:
>  	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
> @@ -3323,6 +3331,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_HYPERV_TLBFLUSH:
>  	case KVM_CAP_HYPERV_SEND_IPI:
>  	case KVM_CAP_HYPERV_CPUID:
> +	case KVM_CAP_HYPERV_DEBUGGING:
>  	case KVM_CAP_PCI_SEGMENT:
>  	case KVM_CAP_DEBUGREGS:
>  	case KVM_CAP_X86_ROBUST_SINGLESTEP:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 9b4d449f4d20..ca28ea04d1d5 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -188,6 +188,7 @@ struct kvm_s390_cmma_log {
>  struct kvm_hyperv_exit {
>  #define KVM_EXIT_HYPERV_SYNIC          1
>  #define KVM_EXIT_HYPERV_HCALL          2
> +#define KVM_EXIT_HYPERV_SYNDBG         3
>  	__u32 type;
>  	union {
>  		struct {
> @@ -202,6 +203,14 @@ struct kvm_hyperv_exit {
>  			__u64 params[2];
>  			__u32 pad;
>  		} hcall;
> +		struct {
> +			__u32 msr;
> +			__u64 control;
> +			__u64 status;
> +			__u64 send_page;
> +			__u64 recv_page;
> +			__u64 pending_page;
> +		} syndbg;
>  	} u;
>  };
>  
> @@ -1011,6 +1020,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_ARM_NISV_TO_USER 177
>  #define KVM_CAP_ARM_INJECT_EXT_DABT 178
>  #define KVM_CAP_S390_VCPU_RESETS 179
> +#define KVM_CAP_HYPERV_DEBUGGING 180
>  
>  #ifdef KVM_CAP_IRQ_ROUTING

-- 
Vitaly

RE: [PATCH v2 2/4] x86/kvm/hyper-v: Add support for synthetic debugger capability

[Michael Kelley]

From: Vitaly Kuznetsov <vkuznets@redhat.com>  Sent: Friday, March 6, 2020 7:27 AM
> 
> Jon Doron <arilou@gmail.com> writes:
> 
> > Add support for Hyper-V synthetic debugger (syndbg) interface.
> > The syndbg interface is using MSRs to emulate a way to send/recv packets
> > data.
> >
> > The debug transport dll (kdvm/kdnet) will identify if Hyper-V is enabled
> > and if it supports the synthetic debugger interface it will attempt to
> > use it, instead of trying to initialize a network adapter.
> >
> 
> I would suggest you split TLFS changes into it's own patch so Hyper-V
> folks can ACK (or they can ack the whole patch with KVM changes of
> course :-)

I have contacted the Hyper-V team for clarification of the status
of the synthetic debugging feature and the associated CPUID leaves and
MSRs.  The first statement I got is that these are "deprecated", but I'm
trying to get more specifics about exactly what that means, if they
are going to be removed in a future release.

Michael

> 
> > Signed-off-by: Jon Doron <arilou@gmail.com>
> > ---
> >  arch/x86/include/asm/hyperv-tlfs.h |  16 ++++
> >  arch/x86/include/asm/kvm_host.h    |  13 ++++
> >  arch/x86/kvm/hyperv.c              | 114 ++++++++++++++++++++++++++++-
> >  arch/x86/kvm/hyperv.h              |   5 ++
> >  arch/x86/kvm/trace.h               |  25 +++++++
> >  arch/x86/kvm/x86.c                 |   9 +++
> >  include/uapi/linux/kvm.h           |  10 +++
> >  7 files changed, 191 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> > index 92abc1e42bfc..8efdf974c23f 100644
> > --- a/arch/x86/include/asm/hyperv-tlfs.h
> > +++ b/arch/x86/include/asm/hyperv-tlfs.h
> > @@ -33,6 +33,9 @@
> >  #define HYPERV_CPUID_ENLIGHTMENT_INFO		0x40000004
> >  #define HYPERV_CPUID_IMPLEMENT_LIMITS		0x40000005
> >  #define HYPERV_CPUID_NESTED_FEATURES		0x4000000A
> > +#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
> > +#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
> > +#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
> >
> >  #define HYPERV_HYPERVISOR_PRESENT_BIT		0x80000000
> >  #define HYPERV_CPUID_MIN			0x40000005
> > @@ -131,6 +134,8 @@
> >  #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE		BIT(8)
> >  /* Crash MSR available */
> >  #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE		BIT(10)
> > +/* Support for debug MSRs available */
> > +#define HV_FEATURE_DEBUG_MSRS_AVAILABLE			BIT(11)
> >  /* stimer Direct Mode is available */
> >  #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
> >
> > @@ -194,6 +199,9 @@
> >  #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
> >  #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
> >
> > +/* Hyper-V synthetic debugger platform capabilities */
> > +#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
> > +
> 
> hyperv-tlfs.h is not perfectly structured but still there is some
> structure there,
> e.g. HV_X64_NESTED_GUEST_MAPPING_FLUSH/HV_X64_NESTED_MSR_BITMAP/... are
> said to be HYPERV_CPUID_ENLIGHTMENT_INFO.EAX
> bits (see above HV_X64_AS_SWITCH_RECOMMENDED).
> 
> To make it clear that HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING doesn't
> belong to these bits I'd suggest you add a comment like
> 
> /*
>  * Hyper-V synthetic debugger platform capabilities.
>  * These are HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits.
>  *
> */
> 
> to make it clear.
> 
> >  /* Hyper-V specific model specific registers (MSRs) */
> >
> >  /* MSR used to identify the guest OS. */
> > @@ -267,6 +275,14 @@
> >  /* Hyper-V guest idle MSR */
> >  #define HV_X64_MSR_GUEST_IDLE			0x400000F0
> >
> > +/* Hyper-V Synthetic debug options MSR */
> > +#define HV_X64_MSR_SYNDBG_CONTROL		0x400000F1
> > +#define HV_X64_MSR_SYNDBG_STATUS		0x400000F2
> > +#define HV_X64_MSR_SYNDBG_SEND_BUFFER		0x400000F3
> > +#define HV_X64_MSR_SYNDBG_RECV_BUFFER		0x400000F4
> > +#define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
> > +#define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
> > +
> >  /* Hyper-V guest crash notification MSR's */
> >  #define HV_X64_MSR_CRASH_P0			0x40000100
> >  #define HV_X64_MSR_CRASH_P1			0x40000101

Re: [PATCH v2 2/4] x86/kvm/hyper-v: Add support for synthetic debugger capability

[Jon Doron]

On 06/03/2020, Vitaly Kuznetsov wrote:
>Jon Doron <arilou@gmail.com> writes:
>
>> Add support for Hyper-V synthetic debugger (syndbg) interface.
>> The syndbg interface is using MSRs to emulate a way to send/recv packets
>> data.
>>
>> The debug transport dll (kdvm/kdnet) will identify if Hyper-V is enabled
>> and if it supports the synthetic debugger interface it will attempt to
>> use it, instead of trying to initialize a network adapter.
>>
>
>I would suggest you split TLFS changes into it's own patch so Hyper-V
>folks can ACK (or they can ack the whole patch with KVM changes of
>course :-)
>

Done.

>> Signed-off-by: Jon Doron <arilou@gmail.com>
>> ---
>>  arch/x86/include/asm/hyperv-tlfs.h |  16 ++++
>>  arch/x86/include/asm/kvm_host.h    |  13 ++++
>>  arch/x86/kvm/hyperv.c              | 114 ++++++++++++++++++++++++++++-
>>  arch/x86/kvm/hyperv.h              |   5 ++
>>  arch/x86/kvm/trace.h               |  25 +++++++
>>  arch/x86/kvm/x86.c                 |   9 +++
>>  include/uapi/linux/kvm.h           |  10 +++
>>  7 files changed, 191 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
>> index 92abc1e42bfc..8efdf974c23f 100644
>> --- a/arch/x86/include/asm/hyperv-tlfs.h
>> +++ b/arch/x86/include/asm/hyperv-tlfs.h
>> @@ -33,6 +33,9 @@
>>  #define HYPERV_CPUID_ENLIGHTMENT_INFO		0x40000004
>>  #define HYPERV_CPUID_IMPLEMENT_LIMITS		0x40000005
>>  #define HYPERV_CPUID_NESTED_FEATURES		0x4000000A
>> +#define HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS	0x40000080
>> +#define HYPERV_CPUID_SYNDBG_INTERFACE			0x40000081
>> +#define HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	0x40000082
>>
>>  #define HYPERV_HYPERVISOR_PRESENT_BIT		0x80000000
>>  #define HYPERV_CPUID_MIN			0x40000005
>> @@ -131,6 +134,8 @@
>>  #define HV_FEATURE_FREQUENCY_MSRS_AVAILABLE		BIT(8)
>>  /* Crash MSR available */
>>  #define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE		BIT(10)
>> +/* Support for debug MSRs available */
>> +#define HV_FEATURE_DEBUG_MSRS_AVAILABLE			BIT(11)
>>  /* stimer Direct Mode is available */
>>  #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
>>
>> @@ -194,6 +199,9 @@
>>  #define HV_X64_NESTED_GUEST_MAPPING_FLUSH		BIT(18)
>>  #define HV_X64_NESTED_MSR_BITMAP			BIT(19)
>>
>> +/* Hyper-V synthetic debugger platform capabilities */
>> +#define HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING	BIT(1)
>> +
>
>hyperv-tlfs.h is not perfectly structured but still there is some
>structure there,
>e.g. HV_X64_NESTED_GUEST_MAPPING_FLUSH/HV_X64_NESTED_MSR_BITMAP/... are
>said to be HYPERV_CPUID_ENLIGHTMENT_INFO.EAX
>bits (see above HV_X64_AS_SWITCH_RECOMMENDED).
>
>To make it clear that HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING doesn't
>belong to these bits I'd suggest you add a comment like
>
>/*
> * Hyper-V synthetic debugger platform capabilities.
> * These are HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX bits.
> *
>*/
>
>to make it clear.
>

Done.

>>  /* Hyper-V specific model specific registers (MSRs) */
>>
>>  /* MSR used to identify the guest OS. */
>> @@ -267,6 +275,14 @@
>>  /* Hyper-V guest idle MSR */
>>  #define HV_X64_MSR_GUEST_IDLE			0x400000F0
>>
>> +/* Hyper-V Synthetic debug options MSR */
>> +#define HV_X64_MSR_SYNDBG_CONTROL		0x400000F1
>> +#define HV_X64_MSR_SYNDBG_STATUS		0x400000F2
>> +#define HV_X64_MSR_SYNDBG_SEND_BUFFER		0x400000F3
>> +#define HV_X64_MSR_SYNDBG_RECV_BUFFER		0x400000F4
>> +#define HV_X64_MSR_SYNDBG_PENDING_BUFFER	0x400000F5
>> +#define HV_X64_MSR_SYNDBG_OPTIONS		0x400000FF
>> +
>>  /* Hyper-V guest crash notification MSR's */
>>  #define HV_X64_MSR_CRASH_P0			0x40000100
>>  #define HV_X64_MSR_CRASH_P1			0x40000101
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 98959e8cd448..f8e58e8866bb 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -854,6 +854,18 @@ struct kvm_apic_map {
>>  	struct kvm_lapic *phys_map[];
>>  };
>>
>> +/* Hyper-V synthetic debugger (SynDbg)*/
>> +struct kvm_hv_syndbg {
>> +	struct {
>> +		u64 control;
>> +		u64 status;
>> +		u64 send_page;
>> +		u64 recv_page;
>> +		u64 pending_page;
>> +	} control;
>> +	u64 options;
>> +};
>> +
>>  /* Hyper-V emulation context */
>>  struct kvm_hv {
>>  	struct mutex hv_lock;
>> @@ -877,6 +889,7 @@ struct kvm_hv {
>>  	atomic_t num_mismatched_vp_indexes;
>>
>>  	struct hv_partition_assist_pg *hv_pa_pg;
>> +	struct kvm_hv_syndbg hv_syndbg;
>>  };
>>
>>  enum kvm_irqchip_mode {
>> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>> index a86fda7a1d03..7cbc4afe9d07 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
>> @@ -266,6 +266,71 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
>>  	return ret;
>>  }
>>
>> +static int kvm_hv_syndbg_complete_userspace(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm *kvm = vcpu->kvm;
>> +	struct kvm_hv *hv = &kvm->arch.hyperv;
>> +
>> +	if (vcpu->run->hyperv.u.syndbg.msr == HV_X64_MSR_SYNDBG_CONTROL)
>> +		hv->hv_syndbg.control.status =
>> +			vcpu->run->hyperv.u.syndbg.status;
>> +	return 1;
>> +}
>> +
>> +static void syndbg_exit(struct kvm_vcpu *vcpu, u32 msr)
>> +{
>> +	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
>> +	struct kvm_vcpu_hv *hv_vcpu = &vcpu->arch.hyperv;
>> +
>> +	hv_vcpu->exit.type = KVM_EXIT_HYPERV_SYNDBG;
>> +	hv_vcpu->exit.u.syndbg.msr = msr;
>> +	hv_vcpu->exit.u.syndbg.control = syndbg->control.control;
>> +	hv_vcpu->exit.u.syndbg.send_page = syndbg->control.send_page;
>> +	hv_vcpu->exit.u.syndbg.recv_page = syndbg->control.recv_page;
>> +	hv_vcpu->exit.u.syndbg.pending_page = syndbg->control.pending_page;
>> +	vcpu->arch.complete_userspace_io =
>> +			kvm_hv_syndbg_complete_userspace;
>> +
>> +	kvm_make_request(KVM_REQ_HV_EXIT, vcpu);
>> +}
>> +
>> +static int syndbg_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>> +{
>> +	struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
>> +	int ret;
>> +
>> +	trace_kvm_hv_syndbg_set_msr(vcpu->vcpu_id,
>> +				    vcpu_to_hv_vcpu(vcpu)->vp_index, msr, data);
>> +	ret = 0;
>> +	switch (msr) {
>> +	case HV_X64_MSR_SYNDBG_CONTROL:
>> +		syndbg->control.control = data;
>> +		syndbg_exit(vcpu, msr);
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_STATUS:
>> +		syndbg->control.status = data;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
>> +		syndbg->control.send_page = data;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
>> +		syndbg->control.recv_page = data;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>> +		syndbg->control.pending_page = data;
>> +		syndbg_exit(vcpu, msr);
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>> +		syndbg->options = data;
>> +		break;
>> +	default:
>> +		ret = 1;
>> +		break;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>>  static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
>>  			 bool host)
>>  {
>> @@ -800,6 +865,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
>>  	case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
>>  	case HV_X64_MSR_TSC_EMULATION_CONTROL:
>>  	case HV_X64_MSR_TSC_EMULATION_STATUS:
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>>  		r = true;
>>  		break;
>>  	}
>> @@ -1061,6 +1128,9 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
>>  		if (!host)
>>  			return 1;
>>  		break;
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>> +		return syndbg_set_msr(vcpu, msr, data);
>>  	default:
>>  		vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n",
>>  			    msr, data);
>> @@ -1227,6 +1297,24 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>>  	case HV_X64_MSR_TSC_EMULATION_STATUS:
>>  		data = hv->hv_tsc_emulation_status;
>>  		break;
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>> +		data = hv->hv_syndbg.options;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_CONTROL:
>> +		data = hv->hv_syndbg.control.control;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_STATUS:
>> +		data = hv->hv_syndbg.control.status;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_SEND_BUFFER:
>> +		data = hv->hv_syndbg.control.send_page;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_RECV_BUFFER:
>> +		data = hv->hv_syndbg.control.recv_page;
>> +		break;
>> +	case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>> +		data = hv->hv_syndbg.control.pending_page;
>> +		break;
>>  	default:
>>  		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
>>  		return 1;
>> @@ -1797,6 +1885,9 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>>  		{ .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
>>  		{ .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
>>  		{ .function = HYPERV_CPUID_NESTED_FEATURES },
>> +		{ .function = HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS },
>> +		{ .function = HYPERV_CPUID_SYNDBG_INTERFACE },
>> +		{ .function = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES	},
>>  	};
>>  	int i, nent = ARRAY_SIZE(cpuid_entries);
>>
>> @@ -1821,7 +1912,7 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>>  		case HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS:
>>  			memcpy(signature, "Linux KVM Hv", 12);
>>
>> -			ent->eax = HYPERV_CPUID_NESTED_FEATURES;
>> +			ent->eax = HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES;
>>  			ent->ebx = signature[0];
>>  			ent->ecx = signature[1];
>>  			ent->edx = signature[2];
>> @@ -1856,9 +1947,12 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>>
>>  			ent->ebx |= HV_X64_POST_MESSAGES;
>>  			ent->ebx |= HV_X64_SIGNAL_EVENTS;
>> +			ent->ebx |= HV_X64_DEBUGGING;
>>
>>  			ent->edx |= HV_FEATURE_FREQUENCY_MSRS_AVAILABLE;
>>  			ent->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
>> +			ent->edx |= HV_X64_GUEST_DEBUGGING_AVAILABLE;
>> +			ent->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
>>
>>  			/*
>>  			 * Direct Synthetic timers only make sense with in-kernel
>> @@ -1903,6 +1997,24 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
>>
>>  			break;
>>
>> +		case HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS:
>> +			memcpy(signature, "Linux KVM Hv", 12);
>> +
>> +			ent->eax = 0;
>> +			ent->ebx = signature[0];
>> +			ent->ecx = signature[1];
>> +			ent->edx = signature[2];
>
>or maybe just copy HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS.EBX if it's not
>any different?
>

So few things about this, HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS 
should return "Microsoft VS" and EAX 0, while
HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS should return "Microsoft Hv" with
EAX as MAX CPUID leaf, with that said the implementation would look 
pretty weird, it would look something like
ent->ebx = cpuid_entries[0].ebx;
...
I thought it's a bit confusing that I'll be addressing the index and 
make the order of the entries in cpuid_entries important.

>> +			break;
>> +
>> +		case HYPERV_CPUID_SYNDBG_INTERFACE:
>> +			memcpy(signature, "VS#1\0\0\0\0\0\0\0\0", 12);
>> +			ent->eax = signature[0];
>> +			break;
>> +
>> +		case HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES:
>> +			ent->eax |= HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
>> +			break;
>> +
>>  		default:
>>  			break;
>>  		}
>> diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
>> index 757cb578101c..6a86151fac53 100644
>> --- a/arch/x86/kvm/hyperv.h
>> +++ b/arch/x86/kvm/hyperv.h
>> @@ -46,6 +46,11 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
>>  	return hv_vcpu_to_vcpu(container_of(synic, struct kvm_vcpu_hv, synic));
>>  }
>>
>> +static inline struct kvm_hv_syndbg *vcpu_to_hv_syndbg(struct kvm_vcpu *vcpu)
>> +{
>> +	return &vcpu->kvm->arch.hyperv.hv_syndbg;
>> +}
>> +
>>  int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
>>  int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
>>
>> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
>> index f194dd058470..5fd600916fd4 100644
>> --- a/arch/x86/kvm/trace.h
>> +++ b/arch/x86/kvm/trace.h
>> @@ -1515,6 +1515,31 @@ TRACE_EVENT(kvm_nested_vmenter_failed,
>>  		__print_symbolic(__entry->err, VMX_VMENTER_INSTRUCTION_ERRORS))
>>  );
>>
>> +/*
>> + * Tracepoint for syndbg_set_msr.
>> + */
>> +TRACE_EVENT(kvm_hv_syndbg_set_msr,
>> +	TP_PROTO(int vcpu_id, u32 vp_index, u32 msr, u64 data),
>> +	TP_ARGS(vcpu_id, vp_index, msr, data),
>> +
>> +	TP_STRUCT__entry(
>> +		__field(int, vcpu_id)
>> +		__field(u32, vp_index)
>> +		__field(u32, msr)
>> +		__field(u64, data)
>> +	),
>> +
>> +	TP_fast_assign(
>> +		__entry->vcpu_id = vcpu_id;
>> +		__entry->vp_index = vp_index;
>> +		__entry->msr = msr;
>> +		__entry->data = data;
>> +	),
>> +
>> +	TP_printk("vcpu_id %d vp_index %u msr 0x%x data 0x%llx",
>> +		  __entry->vcpu_id, __entry->vp_index, __entry->msr,
>> +		  __entry->data)
>> +);
>
>To be consistent, do we also want a kvm_hv_syndbg_get_msr tracepoint?
>

Done.

>>  #endif /* _TRACE_KVM_H */
>>
>>  #undef TRACE_INCLUDE_PATH
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 5de200663f51..619c24bac79e 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -1214,6 +1214,10 @@ static const u32 emulated_msrs_all[] = {
>>  	HV_X64_MSR_VP_ASSIST_PAGE,
>>  	HV_X64_MSR_REENLIGHTENMENT_CONTROL, HV_X64_MSR_TSC_EMULATION_CONTROL,
>>  	HV_X64_MSR_TSC_EMULATION_STATUS,
>> +	HV_X64_MSR_SYNDBG_OPTIONS,
>> +	HV_X64_MSR_SYNDBG_CONTROL, HV_X64_MSR_SYNDBG_STATUS,
>> +	HV_X64_MSR_SYNDBG_SEND_BUFFER, HV_X64_MSR_SYNDBG_RECV_BUFFER,
>> +	HV_X64_MSR_SYNDBG_PENDING_BUFFER,
>>
>>  	MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
>>  	MSR_KVM_PV_EOI_EN,
>> @@ -2906,6 +2910,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>>  		 */
>>  		break;
>>  	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
>> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>>  	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
>>  	case HV_X64_MSR_CRASH_CTL:
>>  	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
>> @@ -3151,6 +3157,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>>  		msr_info->data = 0x20000000;
>>  		break;
>>  	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
>> +	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
>> +	case HV_X64_MSR_SYNDBG_OPTIONS:
>>  	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
>>  	case HV_X64_MSR_CRASH_CTL:
>>  	case HV_X64_MSR_STIMER0_CONFIG ... HV_X64_MSR_STIMER3_COUNT:
>> @@ -3323,6 +3331,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>>  	case KVM_CAP_HYPERV_TLBFLUSH:
>>  	case KVM_CAP_HYPERV_SEND_IPI:
>>  	case KVM_CAP_HYPERV_CPUID:
>> +	case KVM_CAP_HYPERV_DEBUGGING:
>>  	case KVM_CAP_PCI_SEGMENT:
>>  	case KVM_CAP_DEBUGREGS:
>>  	case KVM_CAP_X86_ROBUST_SINGLESTEP:
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 9b4d449f4d20..ca28ea04d1d5 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -188,6 +188,7 @@ struct kvm_s390_cmma_log {
>>  struct kvm_hyperv_exit {
>>  #define KVM_EXIT_HYPERV_SYNIC          1
>>  #define KVM_EXIT_HYPERV_HCALL          2
>> +#define KVM_EXIT_HYPERV_SYNDBG         3
>>  	__u32 type;
>>  	union {
>>  		struct {
>> @@ -202,6 +203,14 @@ struct kvm_hyperv_exit {
>>  			__u64 params[2];
>>  			__u32 pad;
>>  		} hcall;
>> +		struct {
>> +			__u32 msr;
>> +			__u64 control;
>> +			__u64 status;
>> +			__u64 send_page;
>> +			__u64 recv_page;
>> +			__u64 pending_page;
>> +		} syndbg;
>>  	} u;
>>  };
>>
>> @@ -1011,6 +1020,7 @@ struct kvm_ppc_resize_hpt {
>>  #define KVM_CAP_ARM_NISV_TO_USER 177
>>  #define KVM_CAP_ARM_INJECT_EXT_DABT 178
>>  #define KVM_CAP_S390_VCPU_RESETS 179
>> +#define KVM_CAP_HYPERV_DEBUGGING 180
>>
>>  #ifdef KVM_CAP_IRQ_ROUTING
>
>-- 
>Vitaly
>

Re: [PATCH v2 4/4] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls

[Jon Doron]

On 06/03/2020, Vitaly Kuznetsov wrote:
>Jon Doron <arilou@gmail.com> writes:
>
>> 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              | 17 +++++++++++++++++
>>  2 files changed, 22 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)
>
>Nitpick: please add a comment like
>"These are HV_X64_MSR_SYNDBG_OPTIONS bits"
>just before the definition to make it to bluntly obvious.
>

Done.

>> +
>>  /* 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 d657a312004a..52517e11e643 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
>> @@ -1800,6 +1800,23 @@ 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: {
>> +		struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
>> +		if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
>> +			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>
>In TLFS it is said that only HvResetDebugSession of these three can be
>'fast', others are regular hypercalls. We need to add something like
>
>     if (unlikely(fast && code != HVCALL_RESET_DEBUG_SESSION)) {
>            ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>            break;
>     }
>
>also, I'm not sure HV_STATUS_INVALID_HYPERCALL_INPUT is always the right
>return value as TLFS describes this as
>
>"The rep count was incorrect (for example, a non-zero rep count was
>passed to a non-rep call or a zero rep count was passed to a rep call) or
>a reserved bit in the specified hypercall input value was non-zero."
>
>(we may actually be wrong even for existing hypercalls)
>

You are right I believe in the next version I'm using a more proper 
return code.

>> +			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;
>
>-- 
>Vitaly
>