hv: exception: low prioirity exception inject fix

In current code, there is a logic bug when inject low priority
exceptions.
If guest irq enabled, low priority exception will not be injected to guest.
This patch fix the logic error, if there is no eligible vector before
handling low priority exceptions, then inject low priority exception if
any.

Tracked-On: #2405
Signed-off-by: Binbin Wu <binbin.wu@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>

Author: binbinwu1

hypervisor/arch/x86/virq.c

@@ -113,6 +113,10 @@ void vcpu_make_request(struct acrn_vcpu *vcpu, uint16_t eventid)
 
 /*
  * This function is only for case that APICv/VID is not supported.
+ *
+ * @retval 1 when INT is injected to guest.
+ * @retval 0 when there is no eligible pending vector.
+ * @retval -1 when there is a error.
  */
 static int32_t vcpu_inject_vlapic_int(struct acrn_vcpu *vcpu)
 {
@@ -137,18 +141,23 @@ static int32_t vcpu_inject_vlapic_int(struct acrn_vcpu *vcpu)
 				(vector & 0xFFU));
 
 			vlapic_intr_accepted(vlapic, vector);
-			ret = 0;
+			ret = 1;
 		}
 	}
 
 	return ret;
 }
 
+/*
+ * @retval 1 when INT is injected to guest.
+ * @retval 0 when otherwise
+ */
 static int32_t vcpu_do_pending_extint(const struct acrn_vcpu *vcpu)
 {
 	struct acrn_vm *vm;
 	struct acrn_vcpu *primary;
 	uint32_t vector;
+	int32_t ret = 0;
 
 	vm = vcpu->vm;
 
@@ -165,10 +174,11 @@ static int32_t vcpu_do_pending_extint(const struct acrn_vcpu *vcpu)
 					VMX_INT_INFO_VALID |
 					(vector & 0xFFU));
 			vpic_intr_accepted(vcpu->vm, vector);
+			ret = 1;
 		}
 	}
 
-	return 0;
+	return ret;
 }
 
 /* SDM Vol3 -6.15, Table 6-4 - interrupt and exception classes */
@@ -483,6 +493,11 @@ int32_t acrn_handle_pending_request(struct acrn_vcpu *vcpu)
 	return ret;
 }
 
+/*
+ * @retval 1 1 when INT is injected to guest.
+ * @retval 0 when there is no eligible pending vector.
+ * @retval -1 when there is a error.
+ */
 static inline int32_t acrn_inject_pending_vector(struct acrn_vcpu *vcpu, uint64_t *pending_req_bits)
 {
 	int32_t ret = 0;
@@ -518,12 +533,12 @@ static inline int32_t acrn_inject_pending_vector(struct acrn_vcpu *vcpu, uint64_
 					ret = vcpu_inject_vlapic_int(vcpu);
 				}
 			}
-		} else {
+		}
+
+		/* if there is no eligible vector before this point */
+		if (ret == 0) {
 			/* SDM Vol3 table 6-2, inject lowpri exception */
 			ret = vcpu_inject_lo_exception(vcpu);
-			if (ret != 0) {
-				ret = 0;
-			}
 		}
 	}