KVM: PPC: Add feature bitmap for magic page

We will soon add SR PV support to the shared page, so we need some
infrastructure that allows the guest to query for features KVM exports.

This patch adds a second return value to the magic mapping that
indicated to the guest which features are available.
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/include/asm/kvm_para.h

@@ -47,6 +47,8 @@ struct kvm_vcpu_arch_shared {
 
 #define KVM_FEATURE_MAGIC_PAGE	1
 
+#define KVM_MAGIC_FEAT_SR	(1 << 0)
+
 #ifdef __KERNEL__
 
 #ifdef CONFIG_KVM_GUEST

arch/powerpc/kernel/kvm.c

@@ -266,12 +266,20 @@ static void kvm_patch_ins_wrteei(u32 *inst)
 
 static void kvm_map_magic_page(void *data)
 {
-	kvm_hypercall2(KVM_HC_PPC_MAP_MAGIC_PAGE,
-		       KVM_MAGIC_PAGE,  /* Physical Address */
-		       KVM_MAGIC_PAGE); /* Effective Address */
+	u32 *features = data;
+
+	ulong in[8];
+	ulong out[8];
+
+	in[0] = KVM_MAGIC_PAGE;
+	in[1] = KVM_MAGIC_PAGE;
+
+	kvm_hypercall(in, out, HC_VENDOR_KVM | KVM_HC_PPC_MAP_MAGIC_PAGE);
+
+	*features = out[0];
 }
 
-static void kvm_check_ins(u32 *inst)
+static void kvm_check_ins(u32 *inst, u32 features)
 {
 	u32 _inst = *inst;
 	u32 inst_no_rt = _inst & ~KVM_MASK_RT;
@@ -367,9 +375,10 @@ static void kvm_use_magic_page(void)
 	u32 *p;
 	u32 *start, *end;
 	u32 tmp;
+	u32 features;
 
 	/* Tell the host to map the magic page to -4096 on all CPUs */
-	on_each_cpu(kvm_map_magic_page, NULL, 1);
+	on_each_cpu(kvm_map_magic_page, &features, 1);
 
 	/* Quick self-test to see if the mapping works */
 	if (__get_user(tmp, (u32*)KVM_MAGIC_PAGE)) {
@@ -382,7 +391,7 @@ static void kvm_use_magic_page(void)
 	end = (void*)_etext;
 
 	for (p = start; p < end; p++)
-		kvm_check_ins(p);
+		kvm_check_ins(p, features);
 
 	printk(KERN_INFO "KVM: Live patching for a fast VM %s\n",
 			 kvm_patching_worked ? "worked" : "failed");

arch/powerpc/kvm/powerpc.c

@@ -66,6 +66,8 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 		vcpu->arch.magic_page_pa = param1;
 		vcpu->arch.magic_page_ea = param2;
 
+		r2 = 0;
+
 		r = HC_EV_SUCCESS;
 		break;
 	}
@@ -76,13 +78,14 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 #endif
 
 		/* Second return value is in r4 */
-		kvmppc_set_gpr(vcpu, 4, r2);
 		break;
 	default:
 		r = HC_EV_UNIMPLEMENTED;
 		break;
 	}
 
+	kvmppc_set_gpr(vcpu, 4, r2);
+
 	return r;
 }