KVM: s390: intercepts for diagnose instructions

This patch introduces interpretation of some diagnose instruction intercepts.
Diagnose is our classic architected way of doing a hypercall. This patch
features the following diagnose codes:
- vm storage size, that tells the guest about its memory layout
- time slice end, which is used by the guest to indicate that it waits
  for a lock and thus cannot use up its time slice in a useful way
- ipl functions, which a guest can use to reset and reboot itself

In order to implement ipl functions, we also introduce an exit reason that
causes userspace to perform various resets on the virtual machine. All resets
are described in the principles of operation book, except KVM_S390_RESET_IPL
which causes a reboot of the machine.

Acked-by: Martin Schwidefsky <martin.schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

5 files changed, 73 insertions, 1 deletions

diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
index f3bf11a88bc7..e5221ec0b8e3 100644
--- a/arch/s390/kvm/Makefile
+++ b/arch/s390/kvm/Makefile
@@ -10,5 +10,5 @@ common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o)
 
 EXTRA_CFLAGS += -Ivirt/kvm -Iarch/s390/kvm
 
-kvm-objs := $(common-objs) kvm-s390.o sie64a.o intercept.o interrupt.o priv.o sigp.o
+kvm-objs := $(common-objs) kvm-s390.o sie64a.o intercept.o interrupt.o priv.o sigp.o diag.o
 obj-$(CONFIG_KVM) += kvm.o
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
new file mode 100644
index 000000000000..f639a152869f
--- /dev/null
+++ b/arch/s390/kvm/diag.c
@@ -0,0 +1,67 @@
+/*
+ * diag.c - handling diagnose instructions
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ *
+ *    Author(s): Carsten Otte <cotte@de.ibm.com>
+ *               Christian Borntraeger <borntraeger@de.ibm.com>
+ */
+
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+#include "kvm-s390.h"
+
+static int __diag_time_slice_end(struct kvm_vcpu *vcpu)
+{
+        VCPU_EVENT(vcpu, 5, "%s", "diag time slice end");
+        vcpu->stat.diagnose_44++;
+        vcpu_put(vcpu);
+        schedule();
+        vcpu_load(vcpu);
+        return 0;
+}
+
+static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
+{
+        unsigned int reg = vcpu->arch.sie_block->ipa & 0xf;
+        unsigned long subcode = vcpu->arch.guest_gprs[reg] & 0xffff;
+
+        VCPU_EVENT(vcpu, 5, "diag ipl functions, subcode %lx", subcode);
+        switch (subcode) {
+        case 3:
+                vcpu->run->s390_reset_flags = KVM_S390_RESET_CLEAR;
+                break;
+        case 4:
+                vcpu->run->s390_reset_flags = 0;
+                break;
+        default:
+                return -ENOTSUPP;
+        }
+
+        atomic_clear_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags);
+        vcpu->run->s390_reset_flags |= KVM_S390_RESET_SUBSYSTEM;
+        vcpu->run->s390_reset_flags |= KVM_S390_RESET_IPL;
+        vcpu->run->s390_reset_flags |= KVM_S390_RESET_CPU_INIT;
+        vcpu->run->exit_reason = KVM_EXIT_S390_RESET;
+        VCPU_EVENT(vcpu, 3, "requesting userspace resets %lx",
+          vcpu->run->s390_reset_flags);
+        return -EREMOTE;
+}
+
+int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
+{
+        int code = (vcpu->arch.sie_block->ipb & 0xfff0000) >> 16;
+
+        switch (code) {
+        case 0x44:
+                return __diag_time_slice_end(vcpu);
+        case 0x308:
+                return __diag_ipl_functions(vcpu);
+        default:
+                return -ENOTSUPP;
+        }
+}
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 9f0d8b239436..349581a26103 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -95,6 +95,7 @@ static int handle_lctl(struct kvm_vcpu *vcpu)
 }
 
 static intercept_handler_t instruction_handlers[256] = {
+        [0x83] = kvm_s390_handle_diag,
         [0xae] = kvm_s390_handle_sigp,
         [0xb2] = kvm_s390_handle_priv,
         [0xb7] = handle_lctl,
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c632180739ee..d3b1de83678b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -63,6 +63,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "instruction_sigp_set_arch", VCPU_STAT(instruction_sigp_arch) },
         { "instruction_sigp_set_prefix", VCPU_STAT(instruction_sigp_prefix) },
         { "instruction_sigp_restart", VCPU_STAT(instruction_sigp_restart) },
+        { "diagnose_44", VCPU_STAT(diagnose_44) },
         { NULL }
 };
 
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index e6e5756a0e07..3893cf12eacf 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -58,4 +58,7 @@ 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);
+/* implemented in diag.c */
+int kvm_s390_handle_diag(struct kvm_vcpu *vcpu);
+
 #endif