[PATCH v4 3/5] x86/kvm/hyper-v: Add support for synthetic debugger capability

Jon Doron
2020-03-09T18:20:36Z

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/kvm_host.h | 13 +++
arch/x86/kvm/hyperv.c | 135 +++++++++++++++++++++++++++++++-
arch/x86/kvm/hyperv.h | 5 ++
arch/x86/kvm/trace.h | 51 ++++++++++++
arch/x86/kvm/x86.c | 9 +++
include/uapi/linux/kvm.h | 10 +++
6 files changed, 222 insertions(+), 1 deletion(-)

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..b6a97abe2bc9 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -266,6 +266,107 @@ 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 syndbg_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+{
+ struct kvm_hv_syndbg *syndbg = vcpu_to_hv_syndbg(vcpu);
+ int ret;
+
+ ret = 0;
+ switch (msr) {
+ case HV_X64_MSR_SYNDBG_CONTROL:
+ *pdata = syndbg->control.control;
+ break;
+ case HV_X64_MSR_SYNDBG_STATUS:
+ *pdata = syndbg->control.status;
+ break;
+ case HV_X64_MSR_SYNDBG_SEND_BUFFER:
+ *pdata = syndbg->control.send_page;
+ break;
+ case HV_X64_MSR_SYNDBG_RECV_BUFFER:
+ *pdata = syndbg->control.recv_page;
+ break;
+ case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+ *pdata = syndbg->control.pending_page;
+ break;
+ case HV_X64_MSR_SYNDBG_OPTIONS:
+ *pdata = syndbg->options;
+ break;
+ default:
+ ret = 1;
+ break;
+ }
+
+ trace_kvm_hv_syndbg_get_msr(vcpu->vcpu_id,
+ vcpu_to_hv_vcpu(vcpu)->vp_index, msr,
+ *pdata);
+ return ret;
+}
+
static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
bool host)
{
@@ -800,6 +901,8 @@ 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 +1164,9 @@ 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 +1333,9 @@ 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:
+ case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+ return syndbg_get_msr(vcpu, msr, pdata);
default:
vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
return 1;
@@ -1797,6 +1906,9 @@ 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 +1933,7 @@ 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 +1968,12 @@ 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 +2018,24 @@ 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..bf6c3852868d 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -1515,6 +1515,57 @@ 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)
+);
+
+/*
+ * Tracepoint for syndbg_get_msr.
+ */
+TRACE_EVENT(kvm_hv_syndbg_get_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 7acfd6a2569a..cd813114d8ec 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;
__u32 pad;
union {
@@ -202,6 +203,14 @@ struct kvm_hyperv_exit {
__u64 result;
__u64 params[2];
} 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