hyperv: Add support to process syndbg commands

SynDbg commands can come from two different flows:
1. Hypercalls, in this mode the data being sent is fully
   encapsulated network packets.
2. SynDbg specific MSRs, in this mode only the data that needs to be
   transfered is passed.

Signed-off-by: Jon Doron <arilou@gmail.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220216102500.692781-4-arilou@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 126 insertions, 8 deletions

diff --git a/target/i386/kvm/hyperv-stub.c b/target/i386/kvm/hyperv-stub.c
index 0028527..778ed78 100644
--- a/target/i386/kvm/hyperv-stub.c
+++ b/target/i386/kvm/hyperv-stub.c
@@ -28,6 +28,12 @@ int kvm_hv_handle_exit(X86CPU *cpu, struct kvm_hyperv_exit *exit)
     case KVM_EXIT_HYPERV_HCALL:
         exit->u.hcall.result = HV_STATUS_INVALID_HYPERCALL_CODE;
         return 0;
+    case KVM_EXIT_HYPERV_SYNDBG:
+        if (!hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG)) {
+            return -1;
+        }
+
+        return 0;
     default:
         return -1;
     }
diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
index 26efc1e..9026ef3 100644
--- a/target/i386/kvm/hyperv.c
+++ b/target/i386/kvm/hyperv.c
@@ -81,20 +81,66 @@ int kvm_hv_handle_exit(X86CPU *cpu, struct kvm_hyperv_exit *exit)
     case KVM_EXIT_HYPERV_HCALL: {
         uint16_t code = exit->u.hcall.input & 0xffff;
         bool fast = exit->u.hcall.input & HV_HYPERCALL_FAST;
-        uint64_t param = exit->u.hcall.params[0];
+        uint64_t in_param = exit->u.hcall.params[0];
+        uint64_t out_param = exit->u.hcall.params[1];
 
         switch (code) {
         case HV_POST_MESSAGE:
-            exit->u.hcall.result = hyperv_hcall_post_message(param, fast);
+            exit->u.hcall.result = hyperv_hcall_post_message(in_param, fast);
             break;
         case HV_SIGNAL_EVENT:
-            exit->u.hcall.result = hyperv_hcall_signal_event(param, fast);
+            exit->u.hcall.result = hyperv_hcall_signal_event(in_param, fast);
+            break;
+        case HV_POST_DEBUG_DATA:
+            exit->u.hcall.result =
+                hyperv_hcall_post_dbg_data(in_param, out_param, fast);
+            break;
+        case HV_RETRIEVE_DEBUG_DATA:
+            exit->u.hcall.result =
+                hyperv_hcall_retreive_dbg_data(in_param, out_param, fast);
+            break;
+        case HV_RESET_DEBUG_SESSION:
+            exit->u.hcall.result =
+                hyperv_hcall_reset_dbg_session(out_param);
             break;
         default:
             exit->u.hcall.result = HV_STATUS_INVALID_HYPERCALL_CODE;
         }
         return 0;
     }
+
+    case KVM_EXIT_HYPERV_SYNDBG:
+        if (!hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG)) {
+            return -1;
+        }
+
+        switch (exit->u.syndbg.msr) {
+        case HV_X64_MSR_SYNDBG_CONTROL: {
+            uint64_t control = exit->u.syndbg.control;
+            env->msr_hv_syndbg_control = control;
+            env->msr_hv_syndbg_send_page = exit->u.syndbg.send_page;
+            env->msr_hv_syndbg_recv_page = exit->u.syndbg.recv_page;
+            exit->u.syndbg.status = HV_STATUS_SUCCESS;
+            if (control & HV_SYNDBG_CONTROL_SEND) {
+                exit->u.syndbg.status =
+                    hyperv_syndbg_send(env->msr_hv_syndbg_send_page,
+                            HV_SYNDBG_CONTROL_SEND_SIZE(control));
+            } else if (control & HV_SYNDBG_CONTROL_RECV) {
+                exit->u.syndbg.status =
+                    hyperv_syndbg_recv(env->msr_hv_syndbg_recv_page,
+                            TARGET_PAGE_SIZE);
+            }
+            break;
+        }
+        case HV_X64_MSR_SYNDBG_PENDING_BUFFER:
+            env->msr_hv_syndbg_pending_page = exit->u.syndbg.pending_page;
+            hyperv_syndbg_set_pending_page(env->msr_hv_syndbg_pending_page);
+            break;
+        default:
+            return -1;
+        }
+
+        return 0;
     default:
         return -1;
     }
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 9cf8e03..0bb3176 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -104,6 +104,7 @@ static bool has_msr_hv_synic;
 static bool has_msr_hv_stimer;
 static bool has_msr_hv_frequencies;
 static bool has_msr_hv_reenlightenment;
+static bool has_msr_hv_syndbg_options;
 static bool has_msr_xss;
 static bool has_msr_umwait;
 static bool has_msr_spec_ctrl;
@@ -964,6 +965,14 @@ static struct {
              .bits = HV_DEPRECATING_AEOI_RECOMMENDED}
         }
     },
+    [HYPERV_FEAT_SYNDBG] = {
+        .desc = "Enable synthetic kernel debugger channel (hv-syndbg)",
+        .flags = {
+            {.func = HV_CPUID_FEATURES, .reg = R_EDX,
+             .bits = HV_FEATURE_DEBUG_MSRS_AVAILABLE}
+        },
+        .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED)
+    },
 };
 
 static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,
@@ -1004,8 +1013,8 @@ static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,
 static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs)
 {
     struct kvm_cpuid2 *cpuid;
-    /* 0x40000000..0x40000005, 0x4000000A, 0x40000080..0x40000080 leaves */
-    int max = 10;
+    /* 0x40000000..0x40000005, 0x4000000A, 0x40000080..0x40000082 leaves */
+    int max = 11;
     int i;
     bool do_sys_ioctl;
 
@@ -1118,6 +1127,12 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid_legacy(CPUState *cs)
         entry_feat->eax |= HV_SYNTIMERS_AVAILABLE;
     }
 
+    if (has_msr_hv_syndbg_options) {
+        entry_feat->edx |= HV_GUEST_DEBUGGING_AVAILABLE;
+        entry_feat->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
+        entry_feat->ebx |= HV_PARTITION_DEBUGGING_ALLOWED;
+    }
+
     if (kvm_check_extension(cs->kvm_state,
                             KVM_CAP_HYPERV_TLBFLUSH) > 0) {
         entry_recomm->eax |= HV_REMOTE_TLB_FLUSH_RECOMMENDED;
@@ -1369,12 +1384,22 @@ static int hyperv_fill_cpuids(CPUState *cs,
 {
     X86CPU *cpu = X86_CPU(cs);
     struct kvm_cpuid_entry2 *c;
-    uint32_t cpuid_i = 0;
+    uint32_t signature[3];
+    uint32_t cpuid_i = 0, max_cpuid_leaf = 0;
+
+    max_cpuid_leaf = HV_CPUID_IMPLEMENT_LIMITS;
+    if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS)) {
+        max_cpuid_leaf = MAX(max_cpuid_leaf, HV_CPUID_NESTED_FEATURES);
+    }
+
+    if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG)) {
+        max_cpuid_leaf =
+            MAX(max_cpuid_leaf, HV_CPUID_SYNDBG_PLATFORM_CAPABILITIES);
+    }
 
     c = &cpuid_ent[cpuid_i++];
     c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
-    c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ?
-        HV_CPUID_NESTED_FEATURES : HV_CPUID_IMPLEMENT_LIMITS;
+    c->eax = max_cpuid_leaf;
     c->ebx = cpu->hyperv_vendor_id[0];
     c->ecx = cpu->hyperv_vendor_id[1];
     c->edx = cpu->hyperv_vendor_id[2];
@@ -1453,6 +1478,33 @@ static int hyperv_fill_cpuids(CPUState *cs,
         c->eax = cpu->hyperv_nested[0];
     }
 
+    if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG)) {
+        c = &cpuid_ent[cpuid_i++];
+        c->function = HV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS;
+        c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ?
+            HV_CPUID_NESTED_FEATURES : HV_CPUID_IMPLEMENT_LIMITS;
+        memcpy(signature, "Microsoft VS", 12);
+        c->eax = 0;
+        c->ebx = signature[0];
+        c->ecx = signature[1];
+        c->edx = signature[2];
+
+        c = &cpuid_ent[cpuid_i++];
+        c->function = HV_CPUID_SYNDBG_INTERFACE;
+        memcpy(signature, "VS#1\0\0\0\0\0\0\0\0", 12);
+        c->eax = signature[0];
+        c->ebx = 0;
+        c->ecx = 0;
+        c->edx = 0;
+
+        c = &cpuid_ent[cpuid_i++];
+        c->function = HV_CPUID_SYNDBG_PLATFORM_CAPABILITIES;
+        c->eax = HV_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
+        c->ebx = 0;
+        c->ecx = 0;
+        c->edx = 0;
+    }
+
     return cpuid_i;
 }
 
@@ -2261,6 +2313,9 @@ static int kvm_get_supported_msrs(KVMState *s)
             case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
                 has_msr_hv_reenlightenment = true;
                 break;
+            case HV_X64_MSR_SYNDBG_OPTIONS:
+                has_msr_hv_syndbg_options = true;
+                break;
             case MSR_IA32_SPEC_CTRL:
                 has_msr_spec_ctrl = true;
                 break;
@@ -3178,6 +3233,11 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
                 kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_STATUS,
                                   env->msr_hv_tsc_emulation_status);
             }
+            if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNDBG) &&
+                has_msr_hv_syndbg_options) {
+                kvm_msr_entry_add(cpu, HV_X64_MSR_SYNDBG_OPTIONS,
+                                  hyperv_syndbg_query_options());
+            }
         }
         if (hyperv_feat_enabled(cpu, HYPERV_FEAT_VAPIC)) {
             kvm_msr_entry_add(cpu, HV_X64_MSR_APIC_ASSIST_PAGE,
@@ -3619,6 +3679,9 @@ static int kvm_get_msrs(X86CPU *cpu)
         kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_CONTROL, 0);
         kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_STATUS, 0);
     }
+    if (has_msr_hv_syndbg_options) {
+        kvm_msr_entry_add(cpu, HV_X64_MSR_SYNDBG_OPTIONS, 0);
+    }
     if (has_msr_hv_crash) {
         int j;
 
@@ -3910,6 +3973,9 @@ static int kvm_get_msrs(X86CPU *cpu)
         case HV_X64_MSR_TSC_EMULATION_STATUS:
             env->msr_hv_tsc_emulation_status = msrs[i].data;
             break;
+        case HV_X64_MSR_SYNDBG_OPTIONS:
+            env->msr_hv_syndbg_options = msrs[i].data;
+            break;
         case MSR_MTRRdefType:
             env->mtrr_deftype = msrs[i].data;
             break;