[v4,1/6] better kvm detection

Commit Message

Gerd Hoffmann Aug. 24, 2023, 8:57 a.m. UTC

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 <[e-mail]>
---
 src/fw/paravirt.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

Patch

diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
index fba4e52db684..42abac8460c5 100644
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -53,23 +53,35 @@  inline int qemu_cfg_dma_enabled(void)
  * 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 @@  static void kvmclock_init(void)
     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))