commit be84867613f791ea344d565d65a9ce85238e8533
author Gerd Hoffmann <kraxel@redhat.com> Fri Sep 09 07:45:13 2022 +0200
committer Gerd Hoffmann <kraxel@redhat.com> Thu Aug 24 10:56:21 2023 +0200
tree cd2c4cfc4d30e33b821da4d06cb21b1f8155f861
parent 7a4003be25eae462f3c3d8aad96b57e34dc0c2b8

better kvm detection

In case kvm emulates features of another hypervisor (for example hyperv)
two VMM CPUID blocks will be present, one for the emulated hypervisor
and one for kvm itself.

This patch makes seabios loop over the VMM CPUID blocks to make sure it
will properly detect kvm when multiple blocks are present.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

src/fw/paravirt.c

diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
index fba4e52..42abac8 100644
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -53,23 +53,35 @@
  * should be used to determine that a VM is running under KVM.
  */
 #define KVM_CPUID_SIGNATURE     0x40000000
+static unsigned int kvm_cpuid_base = 0;
 
 static void kvm_detect(void)
 {
+    unsigned int i, max = 0;
     unsigned int eax, ebx, ecx, edx;
     char signature[13];
 
-    cpuid(KVM_CPUID_SIGNATURE, &eax, &ebx, &ecx, &edx);
-    memcpy(signature + 0, &ebx, 4);
-    memcpy(signature + 4, &ecx, 4);
-    memcpy(signature + 8, &edx, 4);
-    signature[12] = 0;
+    for (i = KVM_CPUID_SIGNATURE;; i += 0x100) {
+        eax = 0;
+        cpuid(i, &eax, &ebx, &ecx, &edx);
+        if (eax < i)
+            break;
+        memcpy(signature + 0, &ebx, 4);
+        memcpy(signature + 4, &ecx, 4);
+        memcpy(signature + 8, &edx, 4);
+        signature[12] = 0;
+        dprintf(1, "cpuid 0x%x: eax %x, signature '%s'\n", i, eax, signature);
+        if (strcmp(signature, "KVMKVMKVM") == 0) {
+            kvm_cpuid_base = i;
+            max = eax;
+        }
+    }
 
-    if (strcmp(signature, "KVMKVMKVM") == 0) {
+    if (kvm_cpuid_base) {
         dprintf(1, "Running on KVM\n");
         PlatformRunningOn |= PF_KVM;
-        if (eax >= KVM_CPUID_SIGNATURE + 0x10) {
-            cpuid(KVM_CPUID_SIGNATURE + 0x10, &eax, &ebx, &ecx, &edx);
+        if (max >= kvm_cpuid_base + 0x10) {
+            cpuid(kvm_cpuid_base + 0x10, &eax, &ebx, &ecx, &edx);
             dprintf(1, "kvm: have invtsc, freq %u kHz\n", eax);
             tsctimer_setfreq(eax, "invtsc");
         }
@@ -93,7 +105,7 @@
     if (!runningOnKVM())
         return;
 
-    cpuid(KVM_CPUID_SIGNATURE + 0x01, &eax, &ebx, &ecx, &edx);
+    cpuid(kvm_cpuid_base + 0x01, &eax, &ebx, &ecx, &edx);
     if (eax & (1 <<  KVM_FEATURE_CLOCKSOURCE2))
         msr = MSR_KVM_SYSTEM_TIME_NEW;
     else if (eax & (1 <<  KVM_FEATURE_CLOCKSOURCE))