We now added a new set of clock-related msrs in replacement of the old
ones. In theory, we could just try to use them and get a return value
indicating they do not exist, due to our use of kvm_write_msr_save.
However, kvm clock registration happens very early, and if we ever
try to write to a non-existant MSR, we raise a lethal #GP, since our
idt handlers are not in place yet.
So this patch tests for a cpuid feature exported by the host to
decide which set of msrs are supported.
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 0cffb96..a32710a 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -16,6 +16,10 @@
#define KVM_FEATURE_CLOCKSOURCE 0
#define KVM_FEATURE_NOP_IO_DELAY 1
#define KVM_FEATURE_MMU_OP 2
+/* We could just try to use new msr values, but they are queried very early,
+ * kernel does not have idt handlers yet, and failures are fatal */
+#define KVM_FEATURE_CLOCKSOURCE2 3
static int kvmclock = 1;
+static int kvm_use_new_msrs = 0;