KVM: s390: forward most SIGP orders to user space

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>

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 3ca6e0e9a7695165898f1f0fb2cfbc80d0d300b5..df19837e94d4eb7fe9910d0a7565d5e5cf8401e4 100644 (file)
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -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).

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index b6170520380b68b8048e6b081f18468e18e39656..a2dcd0e099f75f0103cafa15b377b7327fe90c25 100644 (file)
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -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;

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index bfb2b990da9b4bc9a51feb1e9d8d152c02b5f1aa..3677b8ca647fca4a933f04788ddc985ab4423be0 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -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;

diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index 1524be9120addf360563e77cc80f6fa48f0d0d31..23b1e86b212245dcf7a95fb4ab82ab99f8749735 100644 (file)
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -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];

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index adc24a3fd23eacb557bb516b41110a0be7c104d4..37f71c3040c39b6accc9c25c2d3f896da9e8da56 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -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