Re: Kernel panic on current amd64 running under Ubuntu KVM (patch included)

[Alexey E. Suslikov]

Jonathan Gray <jsg <at> jsg.id.au> writes:

> Filling the kernel full of if not really running on hardware
> do something else paths is asking for trouble.  If a hypervisor
> claims to be a specific model of a processor it should not be
> surprised when it gets msrs that processor can handle.
> 
> 

FreeBSD do

--- head/sys/amd64/amd64/initcpu.c      2012/03/30 16:32:41     233702
+++ head/sys/amd64/amd64/initcpu.c      2012/08/07 08:36:10     239125
@@ -91,11 +91,17 @@
         *
         * http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf
         * http://support.amd.com/us/Processor_TechDocs/44739_12h_Rev_Gd.pdf
+        *
+        * Hypervisors do not provide access to the errata MSR,
+        * causing #GP exception on attempt to apply the errata.  The
+        * MSR write shall be done on host and persist globally
+        * anyway, so do not try to do it when under virtualization.
         */
        switch (CPUID_TO_FAMILY(cpu_id)) {
        case 0x10:
        case 0x12:
-               wrmsr(0xc0011029, rdmsr(0xc0011029) | 1);
+               if ((cpu_feature2 & CPUID2_HV) == 0)
+                       wrmsr(0xc0011029, rdmsr(0xc0011029) | 1);
                break;
        }
 }