HV: fix unused warning at RELEASE version

We will get following warnings when build acrn as release version. This patch
fix those warnings.

No functional change.

...
arch/x86/cpu.c: In function ‘stop_cpus’:
arch/x86/cpu.c:727:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (get_cpu_id() == i) /* avoid offline itself */
                    ^~
arch/x86/vtd.c: In function ‘dmar_enable_translation’:
arch/x86/vtd.c:84:12: warning: unused variable ‘start’ [-Wunused-variable]
   uint64_t start = rdtsc();                       \
...
arch/x86/guest/instr_emul.c: In function ‘get_gla’:
arch/x86/guest/instr_emul.c:615:6: warning: variable ‘error’ set but not used [-Wunused-but-set-variable]
  int error;
...

Signed-off-by: Kaige Fu <kaige.fu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: KaigeFu

hypervisor/arch/x86/guest/instr_emul.c

@@ -615,18 +615,15 @@ get_gla(struct vcpu *vcpu, __unused struct vie *vie,
 	int error;
 
 	error = vie_read_register(vcpu, VM_REG_GUEST_CR0, &cr0);
-	ASSERT(error == 0, "%s: error %d getting cr0", __func__, error);
-
-	error = vie_read_register(vcpu, VM_REG_GUEST_RFLAGS, &rflags);
-	ASSERT(error == 0, "%s: error %d getting rflags", __func__, error);
+	error |= vie_read_register(vcpu, VM_REG_GUEST_RFLAGS, &rflags);
+	error |= vm_get_seg_desc(vcpu, seg, &desc);
+	error |= vie_read_register(vcpu, gpr, &val);
 
-	error = vm_get_seg_desc(vcpu, seg, &desc);
-	ASSERT(error == 0, "%s: error %d getting segment descriptor %d",
-	    __func__, error, seg);
-
-	error = vie_read_register(vcpu, gpr, &val);
-	ASSERT(error == 0, "%s: error %d getting register %d", __func__,
-	    error, gpr);
+	if (error) {
+		pr_err("%s: error(%d) happens when getting cr0/rflags/segment"
+			"desc/gpr", __func__, error);
+		return -1;
+	}
 
 	if (vie_calculate_gla(paging->cpu_mode, seg, &desc, val, opsize,
 	    addrsize, prot, gla)) {

hypervisor/arch/x86/vtd.c

@@ -81,7 +81,8 @@
 
 #define DMAR_WAIT_COMPLETION(offset, condition, status) \
 	do {                                                \
-		uint64_t start = rdtsc();                       \
+                /* variable start isn't used when built as release version */ \
+		__unused uint64_t start = rdtsc();             \
 		while (1) {                                     \
 			status = iommu_read32(dmar_uint, offset);   \
 			if (condition)                              \