From cb6463d803dfee4ee3f0e6b9158dc241b2fae1b9 Mon Sep 17 00:00:00 2001
From: Jiri Denemark <jdenemar@redhat.com>
Date: Fri, 22 Nov 2024 19:09:39 +0100
Subject: [PATCH] cpu_x86: Record relations between CPU models
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Record a fact a specific CPU model was derived from another one. The
original model is also marked as an alias of the new one in case it did
not change any properties of the original CPU.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/cpu/cpu_x86.c | 47 +++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index 285b272ce8..ce3506be55 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -180,6 +180,17 @@ struct _virCPUx86Model {
      * The corresponding features are a genuine part of the new model.
      */
     GStrv addedFeatures;
+
+    /* Pinter to the model this one was derived from. */
+    virCPUx86Model *ancestor;
+
+    /* Pointer to the canonical model if this model is just an alias.
+     * Because the aliases were actually added to the CPU map before their
+     * canonical models, we store this relation in the XML reversed. That is,
+     * this model contains all the data and the canonical model is defined
+     * using this model as an ancestor without adding any additional data.
+     */
+    const virCPUx86Model *canonical;
 };
 
 typedef struct _virCPUx86Map virCPUx86Map;
@@ -1567,6 +1578,7 @@ x86ModelParseAncestor(virCPUx86Model *model,
         return -1;
     }
 
+    model->ancestor = ancestor;
     model->vendor = ancestor->vendor;
     model->signatures = virCPUx86SignaturesCopy(ancestor->signatures);
     x86DataCopy(&model->data, &ancestor->data);
@@ -1582,9 +1594,11 @@ x86ModelParseAncestor(virCPUx86Model *model,
 }
 
 
+/* Updates @changed if signatures are set. */
 static int
 x86ModelParseSignatures(virCPUx86Model *model,
-                        xmlXPathContextPtr ctxt)
+                        xmlXPathContextPtr ctxt,
+                        bool *changed)
 {
     g_autofree xmlNodePtr *nodes = NULL;
     VIR_XPATH_NODE_AUTORESTORE(ctxt)
@@ -1628,14 +1642,17 @@ x86ModelParseSignatures(virCPUx86Model *model,
             return -1;
     }
 
+    *changed = true;
     return 0;
 }
 
 
+/* Updates @changed if vendor changes. */
 static int
 x86ModelParseVendor(virCPUx86Model *model,
                     xmlXPathContextPtr ctxt,
-                    virCPUx86Map *map)
+                    virCPUx86Map *map,
+                    bool *changed)
 {
     g_autofree char *vendor = NULL;
     int rc;
@@ -1658,14 +1675,17 @@ x86ModelParseVendor(virCPUx86Model *model,
         return -1;
     }
 
+    *changed = true;
     return 0;
 }
 
 
+/* Updates @changed if features are added. */
 static int
 x86ModelParseFeatures(virCPUx86Model *model,
                       xmlXPathContextPtr ctxt,
-                      virCPUx86Map *map)
+                      virCPUx86Map *map,
+                      bool *changed)
 {
     g_autofree xmlNodePtr *nodes = NULL;
     size_t i;
@@ -1725,6 +1745,7 @@ x86ModelParseFeatures(virCPUx86Model *model,
     model->removedFeatures = g_renew(char *, model->removedFeatures, nremoved + 1);
     model->addedFeatures = g_renew(char *, model->addedFeatures, nadded + 1);
 
+    *changed = true;
     return 0;
 }
 
@@ -1736,6 +1757,7 @@ x86ModelParse(xmlXPathContextPtr ctxt,
 {
     virCPUx86Map *map = data;
     g_autoptr(virCPUx86Model) model = NULL;
+    bool changed = false;
 
     if (x86ModelFind(map, name)) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
@@ -1755,15 +1777,28 @@ x86ModelParse(xmlXPathContextPtr ctxt,
     if (x86ModelParseAncestor(model, ctxt, map) < 0)
         return -1;
 
-    if (x86ModelParseSignatures(model, ctxt) < 0)
+    if (x86ModelParseSignatures(model, ctxt, &changed) < 0)
         return -1;
 
-    if (x86ModelParseVendor(model, ctxt, map) < 0)
+    if (x86ModelParseVendor(model, ctxt, map, &changed) < 0)
         return -1;
 
-    if (x86ModelParseFeatures(model, ctxt, map) < 0)
+    if (x86ModelParseFeatures(model, ctxt, map, &changed) < 0)
         return -1;
 
+    if (model->ancestor && !changed) {
+        if (model->ancestor->canonical) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Cannot set CPU model '%1$s' as canonical name of '%2$s' which is already an alias of '%3$s'"),
+                           model->name,
+                           model->ancestor->name,
+                           model->ancestor->canonical->name);
+            return -1;
+        }
+
+        model->ancestor->canonical = model;
+    }
+
     VIR_APPEND_ELEMENT(map->models, map->nmodels, model);
 
     return 0;