KVM: s390: Replace KVM_REQ_MMU_RELOAD usage with arch specific request

Add an arch request, KVM_REQ_REFRESH_GUEST_PREFIX, to deal with guest
prefix changes instead of piggybacking KVM_REQ_MMU_RELOAD.  This will
allow for the removal of the generic KVM_REQ_MMU_RELOAD, which isn't
actually used by generic KVM.

No functional change intended.
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220225182248.3812651-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/s390/include/asm/kvm_host.h

@@ -45,6 +45,8 @@
 #define KVM_REQ_START_MIGRATION KVM_ARCH_REQ(3)
 #define KVM_REQ_STOP_MIGRATION  KVM_ARCH_REQ(4)
 #define KVM_REQ_VSIE_RESTART	KVM_ARCH_REQ(5)
+#define KVM_REQ_REFRESH_GUEST_PREFIX	\
+	KVM_ARCH_REQ_FLAGS(6, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 #define SIGP_CTRL_C		0x80
 #define SIGP_CTRL_SCN_MASK	0x3f

arch/s390/kvm/kvm-s390.c

@@ -3481,7 +3481,7 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
 		if (prefix <= end && start <= prefix + 2*PAGE_SIZE - 1) {
 			VCPU_EVENT(vcpu, 2, "gmap notifier for %lx-%lx",
 				   start, end);
-			kvm_s390_sync_request(KVM_REQ_MMU_RELOAD, vcpu);
+			kvm_s390_sync_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
 		}
 	}
 }
@@ -3883,19 +3883,19 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
 	if (!kvm_request_pending(vcpu))
 		return 0;
 	/*
-	 * We use MMU_RELOAD just to re-arm the ipte notifier for the
+	 * If the guest prefix changed, re-arm the ipte notifier for the
 	 * guest prefix page. gmap_mprotect_notify will wait on the ptl lock.
 	 * This ensures that the ipte instruction for this request has
 	 * already finished. We might race against a second unmapper that
 	 * wants to set the blocking bit. Lets just retry the request loop.
 	 */
-	if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {
+	if (kvm_check_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu)) {
 		int rc;
 		rc = gmap_mprotect_notify(vcpu->arch.gmap,
 					  kvm_s390_get_prefix(vcpu),
 					  PAGE_SIZE * 2, PROT_WRITE);
 		if (rc) {
-			kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
+			kvm_make_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
 			return rc;
 		}
 		goto retry;

arch/s390/kvm/kvm-s390.h

@@ -105,7 +105,7 @@ static inline void kvm_s390_set_prefix(struct kvm_vcpu *vcpu, u32 prefix)
 		   prefix);
 	vcpu->arch.sie_block->prefix = prefix >> GUEST_PREFIX_SHIFT;
 	kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
-	kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
+	kvm_make_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
 }
 
 static inline u64 kvm_s390_get_base_disp_s(struct kvm_vcpu *vcpu, u8 *ar)