virt: if we detect Xen by DMI, trust that over CPUID

Apparently Xen sometimes lies about its identity when queried via CPUID.
Let's hence prefer DMI tests for CPUID

Fixes: #8844

1 files changed, 43 insertions, 35 deletions

diff --git a/src/basic/virt.c b/src/basic/virt.c
index 3b2f1b917..dfa55c710 100644
--- a/src/basic/virt.c
+++ b/src/basic/virt.c
@@ -312,8 +312,8 @@ static int detect_vm_zvm(void) {
 /* Returns a short identifier for the various VM implementations */
 int detect_vm(void) {
         static thread_local int cached_found = _VIRTUALIZATION_INVALID;
-        bool other = false;
         int r, dmi;
+        bool other = false;
 
         if (cached_found >= 0)
                 return cached_found;
@@ -337,19 +337,21 @@ int detect_vm(void) {
         r = detect_vm_cpuid();
         if (r < 0)
                 return r;
-        if (r == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (r != VIRTUALIZATION_NONE)
-                goto finish;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
+        }
 
-        /* Now, let's get back to DMI */
-        if (dmi < 0)
-                return dmi;
-        if (dmi == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (dmi != VIRTUALIZATION_NONE) {
-                r = dmi;
-                goto finish;
+        r = dmi;
+        if (r < 0)
+                return r;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
         }
 
         /* x86 xen will most likely be detected by cpuid. If not (most likely
@@ -361,34 +363,42 @@ int detect_vm(void) {
         r = detect_vm_xen();
         if (r < 0)
                 return r;
-        if (r == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (r != VIRTUALIZATION_NONE)
-                goto finish;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
+        }
 
         r = detect_vm_hypervisor();
         if (r < 0)
                 return r;
-        if (r == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (r != VIRTUALIZATION_NONE)
-                goto finish;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
+        }
 
         r = detect_vm_device_tree();
         if (r < 0)
                 return r;
-        if (r == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (r != VIRTUALIZATION_NONE)
-                goto finish;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
+        }
 
         r = detect_vm_uml();
         if (r < 0)
                 return r;
-        if (r == VIRTUALIZATION_VM_OTHER)
-                other = true;
-        else if (r != VIRTUALIZATION_NONE)
-                goto finish;
+        if (r != VIRTUALIZATION_NONE) {
+                if (r == VIRTUALIZATION_VM_OTHER)
+                        other = true;
+                else
+                        goto finish;
+        }
 
         r = detect_vm_zvm();
         if (r < 0)
@@ -399,12 +409,10 @@ finish:
          * In order to detect the Dom0 as not virtualization we need to
          * double-check it */
         if (r == VIRTUALIZATION_XEN) {
-                int dom0;
-
-                dom0 = detect_vm_xen_dom0();
-                if (dom0 < 0)
-                        return dom0;
-                if (dom0 > 0)
+                int ret = detect_vm_xen_dom0();
+                if (ret < 0)
+                        return ret;
+                if (ret > 0)
                         r = VIRTUALIZATION_NONE;
         } else if (r == VIRTUALIZATION_NONE && other)
                 r = VIRTUALIZATION_VM_OTHER;