From 095760cddc25088cfd5afa7fdaa75ad43c303585 Mon Sep 17 00:00:00 2001
From: Jiri Denemark <jdenemar@redhat.com>
Date: Thu, 16 Jan 2025 13:43:35 +0100
Subject: [PATCH] cpu_x86: Probe host CPU for all MSR features

The list of CPU features we probe from various MSR grew significantly
over time and the CPU map currently mentions 11 distinct MSR indexes.
But the code for directly probing host CPU features was still reading
only the original 0x10a index. Thus the CPU model in host capabilities
was missing a lot of features.

Instead of specifying a static list of indexes to read (which we would
forget to update in the future), let's just read all indexes found in
the CPU map.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
---
 src/cpu/cpu_x86.c | 64 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 9 deletions(-)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index 6d72d446c9..67c88ae3b7 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -2836,15 +2836,63 @@ cpuidSet(uint32_t base, virCPUData *data)
 }
 
 
+static size_t
+virCPUx86ListMSRs(virCPUx86Map *map,
+                  unsigned long **msrs)
+{
+    size_t n = 0;
+    size_t i;
+
+    /* These three nested loops look horrible, but data->len is always 1 here
+     * and thanks to grouping features in the CPU map by their MSR index the
+     * third loop will run more than one iteration only once for each distinct
+     * index.
+     */
+    for (i = 0; i < map->nfeatures; i++) {
+        virCPUx86Data *data = &map->features[i]->data;
+        size_t j;
+
+        for (j = 0; j < data->len; j++) {
+            virCPUx86DataItem *item = &data->items[j];
+            bool found = false;
+            unsigned long msr;
+            size_t k;
+
+            if (item->type != VIR_CPU_X86_DATA_MSR)
+                continue;
+
+            msr = item->data.msr.index;
+
+            for (k = n; k > 0; k--) {
+                if ((*msrs)[k - 1] == msr) {
+                    found = true;
+                    break;
+                }
+            }
+
+            if (!found)
+                VIR_APPEND_ELEMENT(*msrs, n, msr);
+        }
+    }
+
+    return n;
+}
+
+
 static int
 virCPUx86GetHost(virCPUDef *cpu,
                  virDomainCapsCPUModels *models)
 {
     g_autoptr(virCPUData) cpuData = NULL;
     unsigned int addrsz;
+    virCPUx86Map *map;
+    g_autofree unsigned long *msrs = NULL;
+    size_t nmsrs;
+    uint64_t msr;
+    size_t i;
     int ret;
 
-    if (virCPUx86DriverInitialize() < 0)
+    if (!(map = virCPUx86GetMap()))
         return -1;
 
     if (!(cpuData = virCPUDataNew(archs[0])))
@@ -2854,18 +2902,16 @@ virCPUx86GetHost(virCPUDef *cpu,
         cpuidSet(CPUX86_EXTENDED, cpuData) < 0)
         return -1;
 
-    /* Read the IA32_ARCH_CAPABILITIES MSR (0x10a) if supported.
-     * This is best effort since there might be no way to read the MSR
-     * when we are not running as root. */
-    if (virCPUx86DataCheckFeature(cpuData, "arch-capabilities") == 1) {
-        uint64_t msr;
-        unsigned long index = 0x10a;
+    nmsrs = virCPUx86ListMSRs(map, &msrs);
 
-        if (virHostCPUGetMSR(index, &msr) == 0) {
+    /* This is best effort since there might be no way to read the MSR
+     * when we are not running as root. */
+    for (i = 0; i < nmsrs; i++) {
+        if (virHostCPUGetMSR(msrs[i], &msr) == 0) {
             virCPUx86DataItem item = {
                 .type = VIR_CPU_X86_DATA_MSR,
                 .data.msr = {
-                    .index = index,
+                    .index = msrs[i],
                     .eax = msr & 0xffffffff,
                     .edx = msr >> 32,
                 },