hv: add function to reset vcpu registers

This reset_vcpu_regs function will reset the vcpu registers to
default value: realmode with entry 0xFFFFFFF0

Make call to reset_vcpu_regs during create_vcpu and reset_vcpu

Tracked-On: #1231
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: fyin1

hypervisor/arch/x86/guest/vcpu.c

@@ -229,6 +229,29 @@ void set_vcpu_regs(struct vcpu *vcpu, struct acrn_vcpu_regs *vcpu_regs)
 	ctx->cr4 = vcpu_regs->cr4;
 }
 
+static struct acrn_vcpu_regs realmode_init_regs = {
+	.gdt = {
+		.limit = 0xFFFFU,
+		.base = 0UL,
+	},
+	.idt = {
+		.limit = 0xFFFFU,
+		.base = 0UL,
+	},
+	.cs_ar = REAL_MODE_CODE_SEG_AR,
+	.cs_sel = REAL_MODE_BSP_INIT_CODE_SEL,
+	.cs_base = 0xFFFF0000UL,
+	.rip = 0xFFF0UL,
+	.cr0 = CR0_ET | CR0_NE,
+	.cr3 = 0UL,
+	.cr4 = 0UL,
+};
+
+void reset_vcpu_regs(struct vcpu *vcpu)
+{
+	set_vcpu_regs(vcpu, &realmode_init_regs);
+}
+
 /***********************************************************************
  *
  *  @pre vm != NULL && rtn_vcpu_handle != NULL
@@ -314,6 +337,7 @@ int create_vcpu(uint16_t pcpu_id, struct vm *vm, struct vcpu **rtn_vcpu_handle)
 	vcpu->pending_pre_work = 0U;
 	vcpu->state = VCPU_INIT;
 
+	reset_vcpu_regs(vcpu);
 	(void)memset(&vcpu->req, 0U, sizeof(struct io_request));
 
 	return 0;
@@ -486,6 +510,8 @@ void reset_vcpu(struct vcpu *vcpu)
 
 	vlapic = vcpu_vlapic(vcpu);
 	vlapic_reset(vlapic);
+
+	reset_vcpu_regs(vcpu);
 }
 
 void pause_vcpu(struct vcpu *vcpu, enum vcpu_state new_state)

hypervisor/include/arch/x86/guest/vcpu.h

@@ -286,6 +286,7 @@ void vcpu_set_cr4(struct vcpu *vcpu, uint64_t val);
 uint64_t vcpu_get_pat_ext(struct vcpu *vcpu);
 void vcpu_set_pat_ext(struct vcpu *vcpu, uint64_t val);
 void set_vcpu_regs(struct vcpu *vcpu, struct acrn_vcpu_regs *vcpu_regs);
+void reset_vcpu_regs(struct vcpu *vcpu);
 
 static inline bool is_long_mode(struct vcpu *vcpu)
 {