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

ehrhardt
2009-06-15T13:47:54Z

*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;