KVM: Enhance guest cpuid management

The current cpuid management suffers from several problems, which inhibit
passing through the host feature set to the guest:

 - No way to tell which features the host supports

  While some features can be supported with no changes to kvm, others
  need explicit support.  That means kvm needs to vet the feature set
  before it is passed to the guest.

 - No support for indexed or stateful cpuid entries

  Some cpuid entries depend on ecx as well as on eax, or on internal
  state in the processor (running cpuid multiple times with the same
  input returns different output).  The current cpuid machinery only
  supports keying on eax.

 - No support for save/restore/migrate

  The internal state above needs to be exposed to userspace so it can
  be saved or migrated.

This patch adds extended cpuid support by means of three new ioctls:

 - KVM_GET_SUPPORTED_CPUID: get all cpuid entries the host (and kvm)
   supports

 - KVM_SET_CPUID2: sets the vcpu's cpuid table

 - KVM_GET_CPUID2: gets the vcpu's cpuid table, including hidden state

[avi: fix original KVM_SET_CPUID not removing nx on non-nx hosts as it did
      before]

Signed-off-by: Dan Kenigsberg <danken@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/asm-x86/kvm.h b/include/asm-x86/kvm.h
index 4837d75..17afa81 100644
--- a/include/asm-x86/kvm.h
+++ b/include/asm-x86/kvm.h
@@ -151,5 +151,26 @@ struct kvm_cpuid {
 	struct kvm_cpuid_entry entries[0];
 };
 
+struct kvm_cpuid_entry2 {
+	__u32 function;
+	__u32 index;
+	__u32 flags;
+	__u32 eax;
+	__u32 ebx;
+	__u32 ecx;
+	__u32 edx;
+	__u32 padding[3];
+};
+
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX 1
+#define KVM_CPUID_FLAG_STATEFUL_FUNC    2
+#define KVM_CPUID_FLAG_STATE_READ_NEXT  4
+
+/* for KVM_SET_CPUID2 */
+struct kvm_cpuid2 {
+	__u32 nent;
+	__u32 padding;
+	struct kvm_cpuid_entry2 entries[0];
+};
 
 #endif