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s390/kvm: Provide a way to prevent reentering SIE

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Lets provide functions to prevent KVM from reentering SIE and
to kick cpus out of SIE. We cannot use the common kvm_vcpu_kick code,
since we need to kick out guests in places that hold architecture
specific locks (e.g. pgste lock) which might be necessary on the
other cpus - so no waiting possible.

So lets provide a bit in a private field of the sie control block
that acts as a gate keeper, after we claimed we are in SIE.
Please note that we do not reuse prog0c, since we want to access
that bit without atomic ops.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Christian Borntraeger
2013-05-17 14:41:35 +02:00
committed by Gleb Natapov
parent 95d38fd0bc
commit 49b99e1e0d
5 changed files with 40 additions and 2 deletions
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28
arch/s390/kvm/kvm-s390.c
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@@ -454,6 +454,34 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
return 0;
}
void s390_vcpu_block(struct kvm_vcpu *vcpu)
{
atomic_set_mask(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
}
void s390_vcpu_unblock(struct kvm_vcpu *vcpu)
{
atomic_clear_mask(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);
}
/*
* Kick a guest cpu out of SIE and wait until SIE is not running.
* If the CPU is not running (e.g. waiting as idle) the function will
* return immediately. */
void exit_sie(struct kvm_vcpu *vcpu)
{
atomic_set_mask(CPUSTAT_STOP_INT, &vcpu->arch.sie_block->cpuflags);
while (vcpu->arch.sie_block->prog0c & PROG_IN_SIE)
cpu_relax();
}
/* Kick a guest cpu out of SIE and prevent SIE-reentry */
void exit_sie_sync(struct kvm_vcpu *vcpu)
{
s390_vcpu_block(vcpu);
exit_sie(vcpu);
}
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
/* kvm common code refers to this, but never calls it */