[PATCH 3/3] kvm-s390: streamline memslot handling - rebased v2

[ehrhardt@linux.vnet.ibm.com]

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

As requested this is a rebased patch on top of the already applied v3
of the patch series.

*updates to applied version*
- remove dependency to KVM_REQ_MMU_RELOAD in generic code
- remove explicit barrier after test_and_clear_bit as it is implied
- ensure the wait_on_bit waiter is notified
- ensure dropping vcpu all requests while freeing a vcpu
- kickout only scheduled vcpus (its superfluous and wait might hang forever on
  not running vcpus)
- kvm_arch_set_memory_region waits until the bit is consumed by the vcpu

This patch relocates the variables kvm-s390 uses to track guest mem addr/size.
As discussed dropping the variables at struct kvm_arch level allows to use the
common vcpu->request based mechanism to reload guest memory if e.g. changes
via set_memory_region.
The kick mechanism introduced in this series is used to ensure running vcpus
leave guest state to catch the update.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 arch/s390/kvm/kvm-s390.c |   27 ++++++++++++++++++++-------
 arch/s390/kvm/kvm-s390.h |    6 ++++++
 virt/kvm/kvm_main.c      |    6 ++++++
 3 files changed, 32 insertions(+), 7 deletions(-)

Index: kvm/arch/s390/kvm/kvm-s390.c
===================================================================
--- kvm.orig/arch/s390/kvm/kvm-s390.c
+++ kvm/arch/s390/kvm/kvm-s390.c
@@ -674,6 +674,12 @@ long kvm_arch_vcpu_ioctl(struct file *fi
 	return -EINVAL;
 }
 
+static int wait_bit_schedule(void *word)
+{
+	schedule();
+	return 0;
+}
+
 /* Section: memory related */
 int kvm_arch_set_memory_region(struct kvm *kvm,
 				struct kvm_userspace_memory_region *mem,
@@ -681,6 +687,7 @@ int kvm_arch_set_memory_region(struct kv
 				int user_alloc)
 {
 	int i;
+	struct kvm_vcpu *vcpu;
 
 	/* A few sanity checks. We can have exactly one memory slot which has
 	   to start at guest virtual zero and which has to be located at a
@@ -706,13 +713,19 @@ int kvm_arch_set_memory_region(struct kv
 
 	/* request update of sie control block for all available vcpus */
 	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-		if (kvm->vcpus[i]) {
-			if (test_and_set_bit(KVM_REQ_MMU_RELOAD,
-						&kvm->vcpus[i]->requests))
-				continue;
-			kvm_s390_inject_sigp_stop(kvm->vcpus[i],
-						  ACTION_VCPUREQUEST_ON_STOP);
-		}
+		vcpu = kvm->vcpus[i];
+		if (!vcpu)
+			continue;
+
+		if (!test_and_set_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests))
+			continue;
+
+		if (vcpu->cpu == -1)
+			continue;
+
+		kvm_s390_inject_sigp_stop(vcpu, ACTION_VCPUREQUEST_ON_STOP);
+		wait_on_bit(&vcpu->requests, KVM_REQ_MMU_RELOAD,
+			    wait_bit_schedule, TASK_UNINTERRUPTIBLE);
 	}
 
 	return 0;
Index: kvm/arch/s390/kvm/kvm-s390.h
===================================================================
--- kvm.orig/arch/s390/kvm/kvm-s390.h
+++ kvm/arch/s390/kvm/kvm-s390.h
@@ -92,6 +92,12 @@ static inline unsigned long kvm_s390_han
 	if (!vcpu->requests)
 		return 0;
 
+	/* requests that can be handled at all levels */
+	if (test_and_clear_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests)) {
+		wake_up_bit(&vcpu->requests, KVM_REQ_MMU_RELOAD);
+		kvm_s390_vcpu_set_mem(vcpu);
+	}
+
 	return vcpu->requests;
 }
 
Index: kvm/virt/kvm/kvm_main.c
===================================================================
--- kvm.orig/virt/kvm/kvm_main.c
+++ kvm/virt/kvm/kvm_main.c
@@ -1681,6 +1681,12 @@ static int kvm_vcpu_mmap(struct file *fi
 static int kvm_vcpu_release(struct inode *inode, struct file *filp)
 {
 	struct kvm_vcpu *vcpu = filp->private_data;
+	int i;
+
+	vcpu->requests = 0;
+	smp_mb();
+	for (i = 0; i < sizeof(vcpu->requests); i++)
+		wake_up_bit(&vcpu->requests, i);
 
 	kvm_put_kvm(vcpu->kvm);
 	return 0;