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Commit 5a3d883a authored by David Hildenbrand's avatar David Hildenbrand Committed by Christian Borntraeger
Browse files

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



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent 238293b1

arch/s390/kvm/kvm-s390.c

+4 −14
Original line number Diff line number Diff line
@@ -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;

arch/s390/kvm/priv.c

+2 −6
Original line number Diff line number Diff line
@@ -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();