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KVM: s390: forward most SIGP orders to user space

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Most SIGP orders are handled partially in kernel and partially in
user space. In order to:
- Get a correct SIGP SET PREFIX handler that informs user space
- Avoid race conditions between concurrently executed SIGP orders
- Serialize SIGP orders per VCPU

We need to handle all "slow" SIGP orders in user space. The remaining
ones to be handled completely in kernel are:
- SENSE
- SENSE RUNNING
- EXTERNAL CALL
- EMERGENCY SIGNAL
- CONDITIONAL EMERGENCY SIGNAL
According to the PoP, they have to be fast. They can be executed
without conflicting to the actions of other pending/concurrently
executing orders (e.g. STOP vs. START).

This patch introduces a new capability that will - when enabled -
forward all but the mentioned SIGP orders to user space. The
instruction counters in the kernel are still updated.

Reviewed-by: Cornelia Huck <cornelia.huck@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 2014-10-09 14:10:13 +02:00 committed by Christian Borntraeger
parent 9fbd80828c
commit 2444b352c3
5 changed files with 76 additions and 0 deletions
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20
Documentation/virtual/kvm/api.txt
View file

@ -3225,3 +3225,23 @@ userspace from doing that.
If the hcall number specified is not one that has an in-kernel
implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL
error.
7.2 KVM_CAP_S390_USER_SIGP
Architectures: s390
Parameters: none
This capability controls which SIGP orders will be handled completely in user
space. With this capability enabled, all fast orders will be handled completely
in the kernel:
- SENSE
- SENSE RUNNING
- EXTERNAL CALL
- EMERGENCY SIGNAL
- CONDITIONAL EMERGENCY SIGNAL
All other orders will be handled completely in user space.
Only privileged operation exceptions will be checked for in the kernel (or even
in the hardware prior to interception). If this capability is not enabled, the
old way of handling SIGP orders is used (partially in kernel and user space).

1
arch/s390/include/asm/kvm_host.h
View file

@ -521,6 +521,7 @@ struct kvm_arch{
int use_irqchip;
int use_cmma;
int user_cpu_state_ctrl;
int user_sigp;
struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS];
wait_queue_head_t ipte_wq;
int ipte_lock_count;

5
arch/s390/kvm/kvm-s390.c
View file

@ -166,6 +166,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_IRQCHIP:
case KVM_CAP_VM_ATTRIBUTES:
case KVM_CAP_MP_STATE:
case KVM_CAP_S390_USER_SIGP:
r = 1;
break;
case KVM_CAP_NR_VCPUS:
@ -254,6 +255,10 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
kvm->arch.use_irqchip = 1;
r = 0;
break;
case KVM_CAP_S390_USER_SIGP:
kvm->arch.user_sigp = 1;
r = 0;
break;
default:
r = -EINVAL;
break;

49
arch/s390/kvm/sigp.c
View file

@ -371,6 +371,53 @@ static int handle_sigp_dst(struct kvm_vcpu *vcpu, u8 order_code,
return rc;
}
static int handle_sigp_order_in_user_space(struct kvm_vcpu *vcpu, u8 order_code)
{
if (!vcpu->kvm->arch.user_sigp)
return 0;
switch (order_code) {
case SIGP_SENSE:
case SIGP_EXTERNAL_CALL:
case SIGP_EMERGENCY_SIGNAL:
case SIGP_COND_EMERGENCY_SIGNAL:
case SIGP_SENSE_RUNNING:
return 0;
/* update counters as we're directly dropping to user space */
case SIGP_STOP:
vcpu->stat.instruction_sigp_stop++;
break;
case SIGP_STOP_AND_STORE_STATUS:
vcpu->stat.instruction_sigp_stop_store_status++;
break;
case SIGP_STORE_STATUS_AT_ADDRESS:
vcpu->stat.instruction_sigp_store_status++;
break;
case SIGP_SET_PREFIX:
vcpu->stat.instruction_sigp_prefix++;
break;
case SIGP_START:
vcpu->stat.instruction_sigp_start++;
break;
case SIGP_RESTART:
vcpu->stat.instruction_sigp_restart++;
break;
case SIGP_INITIAL_CPU_RESET:
vcpu->stat.instruction_sigp_init_cpu_reset++;
break;
case SIGP_CPU_RESET:
vcpu->stat.instruction_sigp_cpu_reset++;
break;
default:
vcpu->stat.instruction_sigp_unknown++;
}
VCPU_EVENT(vcpu, 4, "sigp order %u: completely handled in user space",
order_code);
return 1;
}
int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu)
{
int r1 = (vcpu->arch.sie_block->ipa & 0x00f0) >> 4;
@ -385,6 +432,8 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu)
return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
order_code = kvm_s390_get_base_disp_rs(vcpu);
if (handle_sigp_order_in_user_space(vcpu, order_code))
return -EOPNOTSUPP;
if (r1 % 2)
parameter = vcpu->run->s.regs.gprs[r1];

1
include/uapi/linux/kvm.h
View file

@ -759,6 +759,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_PPC_FIXUP_HCALL 103
#define KVM_CAP_PPC_ENABLE_HCALL 104
#define KVM_CAP_CHECK_EXTENSION_VM 105
#define KVM_CAP_S390_USER_SIGP 106
#ifdef KVM_CAP_IRQ_ROUTING