commit 60417fcc2b0235dfe3dcd589c56dbe3ea1a64c54
author David Hildenbrand <dahi@linux.vnet.ibm.com> Tue Sep 29 16:20:36 2015 +0200
committer Christian Borntraeger <borntraeger@de.ibm.com> Tue Oct 13 15:50:35 2015 +0200
tree 4e5442dbd7584f8710dd13a3b09eada92dcf0292
parent 25ed16759660cdfccd4a3cb7d30cce8a797b542a

KVM: s390: factor out reading of the guest TOD clock

Let's factor this out and always use get_tod_clock_fast() when
reading the guest TOD.

STORE CLOCK FAST does not do serialization and, therefore, might
result in some fuzziness between different processors in a way
that subsequent calls on different CPUs might have time stamps that
are earlier. This semantics is fine though for all KVM use cases.
To make it obvious that the new function has STORE CLOCK FAST
semantics we name it kvm_s390_get_tod_clock_fast.

With this patch, we only have a handful of places were we
have to care about STP sync (using preempt_disable() logic).

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/interrupt.c

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index a8be542..373e323 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -69,13 +69,8 @@
 
 static int ckc_irq_pending(struct kvm_vcpu *vcpu)
 {
-	preempt_disable();
-	if (!(vcpu->arch.sie_block->ckc <
-	      get_tod_clock_fast() + vcpu->arch.sie_block->epoch)) {
-		preempt_enable();
+	if (vcpu->arch.sie_block->ckc >= kvm_s390_get_tod_clock_fast(vcpu->kvm))
 		return 0;
-	}
-	preempt_enable();
 	return ckc_interrupts_enabled(vcpu);
 }
 
@@ -851,9 +846,7 @@
 		goto no_timer;
 	}
 
-	preempt_disable();
-	now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch;
-	preempt_enable();
+	now = kvm_s390_get_tod_clock_fast(vcpu->kvm);
 	sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
 
 	/* underflow */
@@ -892,9 +885,7 @@
 	u64 now, sltime;
 
 	vcpu = container_of(timer, struct kvm_vcpu, arch.ckc_timer);
-	preempt_disable();
-	now = get_tod_clock_fast() + vcpu->arch.sie_block->epoch;
-	preempt_enable();
+	now = kvm_s390_get_tod_clock_fast(vcpu->kvm);
 	sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
 
 	/*

arch/s390/kvm/kvm-s390.c

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 87bd602f..618c854 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -568,9 +568,7 @@
 {
 	u64 gtod;
 
-	preempt_disable();
-	gtod = get_tod_clock() + kvm->arch.epoch;
-	preempt_enable();
+	gtod = kvm_s390_get_tod_clock_fast(kvm);
 	if (copy_to_user((void __user *)attr->addr, &gtod, sizeof(gtod)))
 		return -EFAULT;
 	VM_EVENT(kvm, 3, "QUERY: TOD base: 0x%llx\n", gtod);

arch/s390/kvm/kvm-s390.h

diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index cc15ea3..1e70e00 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -271,6 +271,16 @@
 		kvm_s390_vcpu_unblock(vcpu);
 }
 
+static inline u64 kvm_s390_get_tod_clock_fast(struct kvm *kvm)
+{
+	u64 rc;
+
+	preempt_disable();
+	rc = get_tod_clock_fast() + kvm->arch.epoch;
+	preempt_enable();
+	return rc;
+}
+
 /**
  * kvm_s390_inject_prog_cond - conditionally inject a program check
  * @vcpu: virtual cpu