KVM: PPC: Add hidden flag for paired singles

The Gekko implements an extension called paired singles. When the guest wants
to use that extension, we need to make sure we're not running the host FPU,
because all FPU instructions need to get emulated to accomodate for additional
operations that occur.

This patch adds an hflag to track if we're in paired single mode or not.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/kvm_asm.h

@@ -88,6 +88,7 @@
 
 #define BOOK3S_HFLAG_DCBZ32			0x1
 #define BOOK3S_HFLAG_SLB			0x2
+#define BOOK3S_HFLAG_PAIRED_SINGLE		0x4
 
 #define RESUME_FLAG_NV          (1<<0)  /* Reload guest nonvolatile state? */
 #define RESUME_FLAG_HOST        (1<<1)  /* Resume host? */

arch/powerpc/kvm/book3s.c

@@ -639,6 +639,10 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr,
 	u64 *thread_fpr = (u64*)t->fpr;
 	int i;
 
+	/* When we have paired singles, we emulate in software */
+	if (vcpu->arch.hflags & BOOK3S_HFLAG_PAIRED_SINGLE)
+		return RESUME_GUEST;
+
 	if (!(vcpu->arch.msr & msr)) {
 		kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
 		return RESUME_GUEST;