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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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5
arch/s390/include/asm/kvm_host.h
View file

@ -71,7 +71,10 @@ struct kvm_s390_sie_block {
__u8 reserved08[4]; /* 0x0008 */
#define PROG_IN_SIE (1<<0)
__u32 prog0c; /* 0x000c */
__u8 reserved10[24]; /* 0x0010 */
__u8 reserved10[16]; /* 0x0010 */
#define PROG_BLOCK_SIE 0x00000001
atomic_t prog20; /* 0x0020 */
__u8 reserved24[4]; /* 0x0024 */
__u64 cputm; /* 0x0028 */
__u64 ckc; /* 0x0030 */
__u64 epoch; /* 0x0038 */

1
arch/s390/kernel/asm-offsets.c
View file

@ -163,6 +163,7 @@ int main(void)
DEFINE(__THREAD_trap_tdb, offsetof(struct task_struct, thread.trap_tdb));
DEFINE(__GMAP_ASCE, offsetof(struct gmap, asce));
DEFINE(__SIE_PROG0C, offsetof(struct kvm_s390_sie_block, prog0c));
DEFINE(__SIE_PROG20, offsetof(struct kvm_s390_sie_block, prog20));
#endif /* CONFIG_32BIT */
return 0;
}

4
arch/s390/kernel/entry64.S
View file

@ -958,7 +958,9 @@ sie_loop:
lctlg %c1,%c1,__GMAP_ASCE(%r14) # load primary asce
sie_gmap:
lg %r14,__SF_EMPTY(%r15) # get control block pointer
oi __SIE_PROG0C+3(%r14),1 # we are in SIE now
oi __SIE_PROG0C+3(%r14),1 # we are going into SIE now
tm __SIE_PROG20+3(%r14),1 # last exit...
jnz sie_done
LPP __SF_EMPTY(%r15) # set guest id
sie 0(%r14)
sie_done:

28
arch/s390/kvm/kvm-s390.c
View file

@ -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 */

4
arch/s390/kvm/kvm-s390.h
View file

@ -133,6 +133,10 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu);
/* implemented in kvm-s390.c */
int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu,
unsigned long addr);
void s390_vcpu_block(struct kvm_vcpu *vcpu);
void s390_vcpu_unblock(struct kvm_vcpu *vcpu);
void exit_sie(struct kvm_vcpu *vcpu);
void exit_sie_sync(struct kvm_vcpu *vcpu);
/* implemented in diag.c */
int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);