[PATCH v3 2/4] KVM: s390: Remove cond_resched() calls

[Heiko Carstens <hca@linux.ibm.com>]

Since [1] cond_resched() is a no-op on s390. Remove all calls.

This also entirely removes uv_call_sched() and replaces all call sites
with uv_call(), since both functions are identical after the removal
of cond_resched().

[1] commit 7dadeaa6e851 ("sched: Further restrict the preemption modes")

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/include/asm/uv.h   | 16 ++--------------
 arch/s390/kernel/uv.c        |  2 +-
 arch/s390/kvm/gaccess.c      |  8 ++------
 arch/s390/kvm/gmap.c         |  4 ----
 arch/s390/kvm/kvm-s390.c     |  1 -
 arch/s390/kvm/pv.c           | 11 +++++------
 arch/s390/kvm/vsie.c         |  1 -
 arch/s390/mm/gmap_helpers.c  |  1 -
 drivers/s390/char/uvdevice.c |  6 +++---
 9 files changed, 13 insertions(+), 37 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index d919e69662f5..89c9bb56c7e6 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -454,18 +454,6 @@ static inline int uv_call(unsigned long r1, unsigned long r2)
 	return cc;
 }
 
-/* Low level uv_call that avoids stalls for long running busy conditions  */
-static inline int uv_call_sched(unsigned long r1, unsigned long r2)
-{
-	int cc;
-
-	do {
-		cc = __uv_call(r1, r2);
-		cond_resched();
-	} while (cc > 1);
-	return cc;
-}
-
 /*
  * special variant of uv_call that only transports the cpu or guest
  * handle and the command, like destroy or verify.
@@ -480,7 +468,7 @@ static inline int uv_cmd_nodata(u64 handle, u16 cmd, u16 *rc, u16 *rrc)
 	int cc;
 
 	WARN(!handle, "No handle provided to Ultravisor call cmd %x\n", cmd);
-	cc = uv_call_sched(0, (u64)&uvcb);
+	cc = uv_call(0, (u64)&uvcb);
 	*rc = uvcb.header.rc;
 	*rrc = uvcb.header.rrc;
 	return cc ? -EINVAL : 0;
@@ -518,7 +506,7 @@ static inline int uv_list_secrets(struct uv_secret_list *buf, u16 start_idx,
 		.start_idx = start_idx,
 		.list_addr = (u64)buf,
 	};
-	int cc = uv_call_sched(0, (u64)&uvcb);
+	int cc = uv_call(0, (u64)&uvcb);
 
 	if (rc)
 		*rc = uvcb.header.rc;
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index a284f98d9716..62841bb00a26 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -831,7 +831,7 @@ int uv_retrieve_secret(u16 secret_idx, u8 *buf, size_t buf_size)
 		.buf_size = buf_size,
 	};
 
-	uv_call_sched(0, (u64)&uvcb);
+	uv_call(0, (u64)&uvcb);
 
 	switch (uvcb.header.rc) {
 	case UVC_RC_EXECUTED:
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 36102b2727fb..0d389a302a70 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -151,10 +151,8 @@ static void ipte_lock_simple(struct kvm *kvm)
 	ic = &kvm->arch.sca->ipte_control;
 	old = READ_ONCE(*ic);
 	do {
-		if (old.k) {
-			cond_resched();
+		if (old.k)
 			goto retry;
-		}
 		new = old;
 		new.k = 1;
 	} while (!try_cmpxchg(&ic->val, &old.val, new.val));
@@ -189,10 +187,8 @@ static void ipte_lock_siif(struct kvm *kvm)
 	ic = &kvm->arch.sca->ipte_control;
 	old = READ_ONCE(*ic);
 	do {
-		if (old.kg) {
-			cond_resched();
+		if (old.kg)
 			goto retry;
-		}
 		new = old;
 		new.k = 1;
 		new.kh++;
diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c
index 8abb4f55b306..3758e4009709 100644
--- a/arch/s390/kvm/gmap.c
+++ b/arch/s390/kvm/gmap.c
@@ -941,7 +941,6 @@ void gmap_split_huge_pages(struct gmap *gmap)
 		scoped_guard(read_lock, &gmap->kvm->mmu_lock)
 			start = _dat_walk_gfn_range(start, asce_end(gmap->asce), gmap->asce,
 						    &ops, DAT_WALK_IGN_HOLES, gmap);
-		cond_resched();
 	} while (start);
 }
 
@@ -963,7 +962,6 @@ static int _gmap_enable_skeys(struct gmap *gmap)
 	do {
 		scoped_guard(write_lock, &gmap->kvm->mmu_lock)
 			start = dat_reset_skeys(gmap->asce, start);
-		cond_resched();
 	} while (start);
 	return 0;
 }
@@ -1019,7 +1017,6 @@ int gmap_pv_destroy_range(struct gmap *gmap, gfn_t start, gfn_t end, bool interr
 						    DAT_WALK_IGN_HOLES, NULL);
 		if (interruptible && fatal_signal_pending(current))
 			return -EINTR;
-		cond_resched();
 	} while (start && start < end);
 	return 0;
 }
@@ -1138,7 +1135,6 @@ void _gmap_set_cmma_all(struct gmap *gmap, bool dirty)
 			gfn = _dat_walk_gfn_range(gfn, asce_end(gmap->asce), gmap->asce, &ops,
 						  DAT_WALK_IGN_HOLES,
 						  &gmap->kvm->arch.cmma_dirty_pages);
-		cond_resched();
 	} while (gfn);
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 150b5dd2170e..2ede8f035a38 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1027,7 +1027,6 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 		do {
 			scoped_guard(read_lock, &kvm->mmu_lock)
 				start_gfn = dat_reset_cmma(kvm->arch.gmap->asce, start_gfn);
-			cond_resched();
 		} while (start_gfn);
 		ret = 0;
 		break;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 1beacc841ca8..54c17ddb6b11 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -429,7 +429,7 @@ static int kvm_s390_pv_deinit_vm_fast(struct kvm *kvm, u16 *rc, u16 *rrc)
 	};
 	int cc;
 
-	cc = uv_call_sched(0, (u64)&uvcb);
+	cc = uv_call(0, (u64)&uvcb);
 	if (rc)
 		*rc = uvcb.header.rc;
 	if (rrc)
@@ -746,7 +746,7 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	}
 	gmap_split_huge_pages(kvm->arch.gmap);
 
-	cc = uv_call_sched(0, (u64)&uvcb);
+	cc = uv_call(0, (u64)&uvcb);
 	*rc = uvcb.header.rc;
 	*rrc = uvcb.header.rrc;
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x flags %04x",
@@ -832,7 +832,6 @@ int kvm_s390_pv_unpack(struct kvm *kvm, unsigned long addr, unsigned long size,
 	while (offset < size) {
 		ret = unpack_one(kvm, addr, tweak, offset, rc, rrc);
 		if (ret == -EAGAIN) {
-			cond_resched();
 			if (fatal_signal_pending(current))
 				break;
 			continue;
@@ -875,7 +874,7 @@ int kvm_s390_pv_dump_cpu(struct kvm_vcpu *vcpu, void *buff, u16 *rc, u16 *rrc)
 	};
 	int cc;
 
-	cc = uv_call_sched(0, (u64)&uvcb);
+	cc = uv_call(0, (u64)&uvcb);
 	*rc = uvcb.header.rc;
 	*rrc = uvcb.header.rrc;
 	return cc;
@@ -959,7 +958,7 @@ int kvm_s390_pv_dump_stor_state(struct kvm *kvm, void __user *buff_user,
 	/* We will loop until the user buffer is filled or an error occurs */
 	do {
 		/* Get 1MB worth of guest storage state data */
-		cc = uv_call_sched(0, (u64)&uvcb);
+		cc = uv_call(0, (u64)&uvcb);
 
 		/* All or nothing */
 		if (cc) {
@@ -1037,7 +1036,7 @@ int kvm_s390_pv_dump_complete(struct kvm *kvm, void __user *buff_user,
 		return -ENOMEM;
 	complete.dump_area_origin = (u64)compl_data;
 
-	ret = uv_call_sched(0, (u64)&complete);
+	ret = uv_call(0, (u64)&complete);
 	*rc = complete.header.rc;
 	*rrc = complete.header.rrc;
 	KVM_UV_EVENT(kvm, 3, "PROTVIRT DUMP COMPLETE: rc %x rrc %x",
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index eea24562e7db..6dcd3b110c17 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1434,7 +1434,6 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		}
 		if (sg)
 			sg = gmap_put(sg);
-		cond_resched();
 	}
 	if (sg)
 		sg = gmap_put(sg);
diff --git a/arch/s390/mm/gmap_helpers.c b/arch/s390/mm/gmap_helpers.c
index 4bf7c9012feb..d564cdefb90f 100644
--- a/arch/s390/mm/gmap_helpers.c
+++ b/arch/s390/mm/gmap_helpers.c
@@ -272,7 +272,6 @@ static int __gmap_helper_unshare_zeropages(struct mm_struct *mm)
 		 * truncation. In that case, the shared zeropage would be gone
 		 * and we can simply retry and make progress.
 		 */
-		cond_resched();
 		goto retry;
 	}
 
diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index e6a264c996ce..4d274a2ee84d 100644
--- a/drivers/s390/char/uvdevice.c
+++ b/drivers/s390/char/uvdevice.c
@@ -224,7 +224,7 @@ static int uvio_attestation(struct uvio_ioctl_cb *uv_ioctl)
 	if (ret)
 		goto out;
 
-	uv_call_sched(0, (u64)uvcb_attest);
+	uv_call(0, (u64)uvcb_attest);
 
 	uv_ioctl->uv_rc = uvcb_attest->header.rc;
 	uv_ioctl->uv_rrc = uvcb_attest->header.rrc;
@@ -291,7 +291,7 @@ static int uvio_add_secret(struct uvio_ioctl_cb *uv_ioctl)
 
 	ret = 0;
 	uvcb.addr = (u64)asrcb;
-	uv_call_sched(0, (u64)&uvcb);
+	uv_call(0, (u64)&uvcb);
 	uv_ioctl->uv_rc = uvcb.header.rc;
 	uv_ioctl->uv_rrc = uvcb.header.rrc;
 
@@ -457,7 +457,7 @@ static int uvio_retr_secret(struct uvio_ioctl_cb *uv_ioctl)
 
 	uvcb.buf_addr = (u64)buf;
 	uvcb.buf_size = buf_len;
-	uv_call_sched(0, (u64)&uvcb);
+	uv_call(0, (u64)&uvcb);
 
 	if (copy_to_user((__user void *)uv_ioctl->argument_addr, buf, buf_len))
 		goto err;
-- 
2.53.0