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KVM: s390: switch to get_tod_clock() and fix STP sync races

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Nobody except early.c makes use of store_tod_clock() to handle the
cc. So if we would get a cc != 0, we would be in more trouble.

Let's replace all users with get_tod_clock(). Returning a cc
on an ioctl sounded strange either way.

We can now also easily move the get_tod_clock() call into the
preempt_disable() section. This is in fact necessary to make the
STP sync work as expected. Otherwise the host TOD could change
and we would end up with a wrong epoch calculation.

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>
This commit is contained in:
David Hildenbrand 2015-09-29 16:27:24 +02:00 committed by Christian Borntraeger
parent 238293b14d
commit 5a3d883a59
2 changed files with 6 additions and 20 deletions
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18
arch/s390/kvm/kvm-s390.c
View File

@ -523,19 +523,14 @@ static int kvm_s390_set_tod_low(struct kvm *kvm, struct kvm_device_attr *attr)
{
struct kvm_vcpu *cur_vcpu;
unsigned int vcpu_idx;
u64 host_tod, gtod;
int r;
u64 gtod;
if (copy_from_user(&gtod, (void __user *)attr->addr, sizeof(gtod)))
return -EFAULT;
r = store_tod_clock(&host_tod);
if (r)
return r;
mutex_lock(&kvm->lock);
preempt_disable();
kvm->arch.epoch = gtod - host_tod;
kvm->arch.epoch = gtod - get_tod_clock();
kvm_s390_vcpu_block_all(kvm);
kvm_for_each_vcpu(vcpu_idx, cur_vcpu, kvm)
cur_vcpu->arch.sie_block->epoch = kvm->arch.epoch;
@ -581,15 +576,10 @@ static int kvm_s390_get_tod_high(struct kvm *kvm, struct kvm_device_attr *attr)
static int kvm_s390_get_tod_low(struct kvm *kvm, struct kvm_device_attr *attr)
{
u64 host_tod, gtod;
int r;
r = store_tod_clock(&host_tod);
if (r)
return r;
u64 gtod;
preempt_disable();
gtod = host_tod + kvm->arch.epoch;
gtod = get_tod_clock() + kvm->arch.epoch;
preempt_enable();
if (copy_to_user((void __user *)attr->addr, &gtod, sizeof(gtod)))
return -EFAULT;

8
arch/s390/kvm/priv.c
View File

@ -34,7 +34,7 @@
static int handle_set_clock(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu *cpup;
s64 hostclk, val;
s64 val;
int i, rc;
ar_t ar;
u64 op2;
@ -49,15 +49,11 @@ static int handle_set_clock(struct kvm_vcpu *vcpu)
if (rc)
return kvm_s390_inject_prog_cond(vcpu, rc);
if (store_tod_clock(&hostclk)) {
kvm_s390_set_psw_cc(vcpu, 3);
return 0;
}
VCPU_EVENT(vcpu, 3, "SCK: setting guest TOD to 0x%llx", val);
val = (val - hostclk) & ~0x3fUL;
mutex_lock(&vcpu->kvm->lock);
preempt_disable();
val = (val - get_tod_clock()) & ~0x3fUL;
kvm_for_each_vcpu(i, cpup, vcpu->kvm)
cpup->arch.sie_block->epoch = val;
preempt_enable();