Fetch standard register state from MSHV vCPUs to support debugging,
migration, and other introspection features in QEMU.

Fetch standard register state from a MHSV vCPU's. A generic get_regs()
function and a mapper to map the different register representations are
introduced.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
---
 include/system/mshv.h       |  1 +
 target/i386/mshv/mshv-cpu.c | 69 +++++++++++++++++++++++++++++++++++--
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/include/system/mshv.h b/include/system/mshv.h
index adce4153d9..65f7fa15a0 100644
--- a/include/system/mshv.h
+++ b/include/system/mshv.h
@@ -88,6 +88,7 @@ typedef enum MshvVmExit {
 void mshv_init_cpu_logic(void);
 int mshv_create_vcpu(int vm_fd, uint8_t vp_index, int *cpu_fd);
 void mshv_remove_vcpu(int vm_fd, int cpu_fd);
+int mshv_get_standard_regs(CPUState *cpu);
 int mshv_run_vcpu(int vm_fd, CPUState *cpu, hv_message *msg, MshvVmExit *exit);
 int mshv_load_regs(CPUState *cpu);
 int mshv_store_regs(CPUState *cpu);
diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c
index 4bd4e29b72..cb59d74eb4 100644
--- a/target/i386/mshv/mshv-cpu.c
+++ b/target/i386/mshv/mshv-cpu.c
@@ -61,6 +61,18 @@ int mshv_set_generic_regs(int cpu_fd, hv_register_assoc *assocs, size_t n_regs)
     return ioctl(cpu_fd, MSHV_SET_VP_REGISTERS, &input);
 }
 
+static int get_generic_regs(int cpu_fd, struct hv_register_assoc *assocs,
+                            size_t n_regs)
+{
+    struct mshv_vp_registers input = {
+        .count = n_regs,
+        .regs = assocs,
+    };
+
+    return ioctl(cpu_fd, MSHV_GET_VP_REGISTERS, &input);
+}
+
+
 static int set_standard_regs(const CPUState *cpu)
 {
     X86CPU *x86cpu = X86_CPU(cpu);
@@ -115,11 +127,64 @@ int mshv_store_regs(CPUState *cpu)
     return 0;
 }
 
+static void populate_standard_regs(const hv_register_assoc *assocs,
+                                   CPUX86State *env)
+{
+    env->regs[R_EAX] = assocs[0].value.reg64;
+    env->regs[R_EBX] = assocs[1].value.reg64;
+    env->regs[R_ECX] = assocs[2].value.reg64;
+    env->regs[R_EDX] = assocs[3].value.reg64;
+    env->regs[R_ESI] = assocs[4].value.reg64;
+    env->regs[R_EDI] = assocs[5].value.reg64;
+    env->regs[R_ESP] = assocs[6].value.reg64;
+    env->regs[R_EBP] = assocs[7].value.reg64;
+    env->regs[R_R8]  = assocs[8].value.reg64;
+    env->regs[R_R9]  = assocs[9].value.reg64;
+    env->regs[R_R10] = assocs[10].value.reg64;
+    env->regs[R_R11] = assocs[11].value.reg64;
+    env->regs[R_R12] = assocs[12].value.reg64;
+    env->regs[R_R13] = assocs[13].value.reg64;
+    env->regs[R_R14] = assocs[14].value.reg64;
+    env->regs[R_R15] = assocs[15].value.reg64;
+
+    env->eip = assocs[16].value.reg64;
+    env->eflags = assocs[17].value.reg64;
+    rflags_to_lflags(env);
+}
+
+int mshv_get_standard_regs(CPUState *cpu)
+{
+    struct hv_register_assoc assocs[ARRAY_SIZE(STANDARD_REGISTER_NAMES)];
+    int ret;
+    X86CPU *x86cpu = X86_CPU(cpu);
+    CPUX86State *env = &x86cpu->env;
+    int cpu_fd = mshv_vcpufd(cpu);
+    size_t n_regs = ARRAY_SIZE(STANDARD_REGISTER_NAMES);
+
+    for (size_t i = 0; i < n_regs; i++) {
+        assocs[i].name = STANDARD_REGISTER_NAMES[i];
+    }
+    ret = get_generic_regs(cpu_fd, assocs, n_regs);
+    if (ret < 0) {
+        error_report("failed to get standard registers");
+        return -1;
+    }
+
+    populate_standard_regs(assocs, env);
+    return 0;
+}
 
 int mshv_load_regs(CPUState *cpu)
 {
-    error_report("unimplemented");
-    abort();
+    int ret;
+
+    ret = mshv_get_standard_regs(cpu);
+    if (ret < 0) {
+        error_report("Failed to load standard registers");
+        return -1;
+    }
+
+    return 0;
 }
 
 int mshv_arch_put_registers(const CPUState *cpu)
-- 
2.34.1