KVM: s390: Add support for channel I/O instructions.

Add a new capability, KVM_CAP_S390_CSS_SUPPORT, which will pass
intercepts for channel I/O instructions to userspace. Only I/O
instructions interacting with I/O interrupts need to be handled
in-kernel:

- TEST PENDING INTERRUPTION (tpi) dequeues and stores pending
  interrupts entirely in-kernel.
- TEST SUBCHANNEL (tsch) dequeues pending interrupts in-kernel
  and exits via KVM_EXIT_S390_TSCH to userspace for subchannel-
  related processing.

Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

7 files changed, 160 insertions, 4 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 29363d155cd5..16bd5d169cdb 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -262,6 +262,7 @@ struct kvm_arch{
         debug_info_t *dbf;
         struct kvm_s390_float_interrupt float_int;
         struct gmap *gmap;
+        int css_support;
 };
 
 extern int sie64a(struct kvm_s390_sie_block *, u64 *);
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 71af87dbb42c..f26ff1e31bdb 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -264,6 +264,7 @@ static const intercept_handler_t intercept_funcs[] = {
         [0x0C >> 2] = handle_instruction_and_prog,
         [0x10 >> 2] = handle_noop,
         [0x14 >> 2] = handle_noop,
+        [0x18 >> 2] = handle_noop,
         [0x1C >> 2] = kvm_s390_handle_wait,
         [0x20 >> 2] = handle_validity,
         [0x28 >> 2] = handle_stop,
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index b3b4748485ee..9a128357fd15 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -709,6 +709,43 @@ int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code)
         return 0;
 }
 
+struct kvm_s390_interrupt_info *kvm_s390_get_io_int(struct kvm *kvm,
+                                                    u64 cr6, u64 schid)
+{
+        struct kvm_s390_float_interrupt *fi;
+        struct kvm_s390_interrupt_info *inti, *iter;
+
+        if ((!schid && !cr6) || (schid && cr6))
+                return NULL;
+        mutex_lock(&kvm->lock);
+        fi = &kvm->arch.float_int;
+        spin_lock(&fi->lock);
+        inti = NULL;
+        list_for_each_entry(iter, &fi->list, list) {
+                if (!is_ioint(iter->type))
+                        continue;
+                if (cr6 && ((cr6 & iter->io.io_int_word) == 0))
+                        continue;
+                if (schid) {
+                        if (((schid & 0x00000000ffff0000) >> 16) !=
+                            iter->io.subchannel_id)
+                                continue;
+                        if ((schid & 0x000000000000ffff) !=
+                            iter->io.subchannel_nr)
+                                continue;
+                }
+                inti = iter;
+                break;
+        }
+        if (inti)
+                list_del_init(&inti->list);
+        if (list_empty(&fi->list))
+                atomic_set(&fi->active, 0);
+        spin_unlock(&fi->lock);
+        mutex_unlock(&kvm->lock);
+        return inti;
+}
+
 int kvm_s390_inject_vm(struct kvm *kvm,
                        struct kvm_s390_interrupt *s390int)
 {
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 5ff26033825c..5b01f0953900 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -141,6 +141,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_SYNC_REGS:
         case KVM_CAP_ONE_REG:
         case KVM_CAP_ENABLE_CAP:
+        case KVM_CAP_S390_CSS_SUPPORT:
                 r = 1;
                 break;
         case KVM_CAP_NR_VCPUS:
@@ -235,6 +236,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
                 if (!kvm->arch.gmap)
                         goto out_nogmap;
         }
+
+        kvm->arch.css_support = 0;
+
         return 0;
 out_nogmap:
         debug_unregister(kvm->arch.dbf);
@@ -658,6 +662,7 @@ rerun_vcpu:
         case KVM_EXIT_INTR:
         case KVM_EXIT_S390_RESET:
         case KVM_EXIT_S390_UCONTROL:
+        case KVM_EXIT_S390_TSCH:
                 break;
         default:
                 BUG();
@@ -818,6 +823,13 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
                 return -EINVAL;
 
         switch (cap->cap) {
+        case KVM_CAP_S390_CSS_SUPPORT:
+                if (!vcpu->kvm->arch.css_support) {
+                        vcpu->kvm->arch.css_support = 1;
+                        trace_kvm_s390_enable_css(vcpu->kvm);
+                }
+                r = 0;
+                break;
         default:
                 r = -EINVAL;
                 break;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 211b340385a7..3e05deff21b6 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -113,6 +113,8 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
                 struct kvm_s390_interrupt *s390int);
 int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code);
 int kvm_s390_inject_sigp_stop(struct kvm_vcpu *vcpu, int action);
+struct kvm_s390_interrupt_info *kvm_s390_get_io_int(struct kvm *kvm,
+                                                    u64 cr6, u64 schid);
 
 /* implemented in priv.c */
 int kvm_s390_handle_b2(struct kvm_vcpu *vcpu);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 8ad776f87856..0ef9894606e5 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -127,15 +127,98 @@ static int handle_skey(struct kvm_vcpu *vcpu)
         return 0;
 }
 
-static int handle_io_inst(struct kvm_vcpu *vcpu)
+static int handle_tpi(struct kvm_vcpu *vcpu)
 {
-        VCPU_EVENT(vcpu, 4, "%s", "I/O instruction");
-        /* condition code 3 */
+        u64 addr;
+        struct kvm_s390_interrupt_info *inti;
+        int cc;
+
+        addr = kvm_s390_get_base_disp_s(vcpu);
+
+        inti = kvm_s390_get_io_int(vcpu->kvm, vcpu->run->s.regs.crs[6], 0);
+        if (inti) {
+                if (addr) {
+                        /*
+                         * Store the two-word I/O interruption code into the
+                         * provided area.
+                         */
+                        put_guest_u16(vcpu, addr, inti->io.subchannel_id);
+                        put_guest_u16(vcpu, addr + 2, inti->io.subchannel_nr);
+                        put_guest_u32(vcpu, addr + 4, inti->io.io_int_parm);
+                } else {
+                        /*
+                         * Store the three-word I/O interruption code into
+                         * the appropriate lowcore area.
+                         */
+                        put_guest_u16(vcpu, 184, inti->io.subchannel_id);
+                        put_guest_u16(vcpu, 186, inti->io.subchannel_nr);
+                        put_guest_u32(vcpu, 188, inti->io.io_int_parm);
+                        put_guest_u32(vcpu, 192, inti->io.io_int_word);
+                }
+                cc = 1;
+        } else
+                cc = 0;
+        kfree(inti);
+        /* Set condition code and we're done. */
         vcpu->arch.sie_block->gpsw.mask &= ~(3ul << 44);
-        vcpu->arch.sie_block->gpsw.mask |= (3 & 3ul) << 44;
+        vcpu->arch.sie_block->gpsw.mask |= (cc & 3ul) << 44;
         return 0;
 }
 
+static int handle_tsch(struct kvm_vcpu *vcpu)
+{
+        struct kvm_s390_interrupt_info *inti;
+
+        inti = kvm_s390_get_io_int(vcpu->kvm, 0,
+                                   vcpu->run->s.regs.gprs[1]);
+
+        /*
+         * Prepare exit to userspace.
+         * We indicate whether we dequeued a pending I/O interrupt
+         * so that userspace can re-inject it if the instruction gets
+         * a program check. While this may re-order the pending I/O
+         * interrupts, this is no problem since the priority is kept
+         * intact.
+         */
+        vcpu->run->exit_reason = KVM_EXIT_S390_TSCH;
+        vcpu->run->s390_tsch.dequeued = !!inti;
+        if (inti) {
+                vcpu->run->s390_tsch.subchannel_id = inti->io.subchannel_id;
+                vcpu->run->s390_tsch.subchannel_nr = inti->io.subchannel_nr;
+                vcpu->run->s390_tsch.io_int_parm = inti->io.io_int_parm;
+                vcpu->run->s390_tsch.io_int_word = inti->io.io_int_word;
+        }
+        vcpu->run->s390_tsch.ipb = vcpu->arch.sie_block->ipb;
+        kfree(inti);
+        return -EREMOTE;
+}
+
+static int handle_io_inst(struct kvm_vcpu *vcpu)
+{
+        VCPU_EVENT(vcpu, 4, "%s", "I/O instruction");
+
+        if (vcpu->kvm->arch.css_support) {
+                /*
+                 * Most I/O instructions will be handled by userspace.
+                 * Exceptions are tpi and the interrupt portion of tsch.
+                 */
+                if (vcpu->arch.sie_block->ipa == 0xb236)
+                        return handle_tpi(vcpu);
+                if (vcpu->arch.sie_block->ipa == 0xb235)
+                        return handle_tsch(vcpu);
+                /* Handle in userspace. */
+                return -EOPNOTSUPP;
+        } else {
+                /*
+                 * Set condition code 3 to stop the guest from issueing channel
+                 * I/O instructions.
+                 */
+                vcpu->arch.sie_block->gpsw.mask &= ~(3ul << 44);
+                vcpu->arch.sie_block->gpsw.mask |= (3 & 3ul) << 44;
+                return 0;
+        }
+}
+
 static int handle_stfl(struct kvm_vcpu *vcpu)
 {
         unsigned int facility_list;
diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
index 95fbc1ab88dc..13f30f58a2df 100644
--- a/arch/s390/kvm/trace-s390.h
+++ b/arch/s390/kvm/trace-s390.h
@@ -204,6 +204,26 @@ TRACE_EVENT(kvm_s390_stop_request,
         );
 
 
+/*
+ * Trace point for enabling channel I/O instruction support.
+ */
+TRACE_EVENT(kvm_s390_enable_css,
+            TP_PROTO(void *kvm),
+            TP_ARGS(kvm),
+
+            TP_STRUCT__entry(
+                    __field(void *, kvm)
+                    ),
+
+            TP_fast_assign(
+                    __entry->kvm = kvm;
+                    ),
+
+            TP_printk("enabling channel I/O support (kvm @ %p)\n",
+                      __entry->kvm)
+        );
+
+
 #endif /* _TRACE_KVMS390_H */
 
 /* This part must be outside protection */