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>

1 files changed, 87 insertions, 4 deletions

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;