s390x/ipl: support diagnose 308 subcodes 5 and 6

To support dynamically updating the IPL device from inside the KVM
guest on the s390 platform, DIAG 308 instruction is intercepted
in QEMU to handle the request.

Subcode 5 allows to specify a new boot device, which is saved for
later in the s390_ipl device. This also allows to switch from an
external kernel to a boot device.

Subcode 6 retrieves boot device configuration that has been previously
set.

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Fan Zhang <zhangfan@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

hw/s390x/ipl.c

@@ -18,6 +18,7 @@
 #include "hw/sysbus.h"
 #include "hw/s390x/virtio-ccw.h"
 #include "hw/s390x/css.h"
+#include "ipl.h"
 
 #define KERN_IMAGE_START                0x010000UL
 #define KERN_PARM_AREA                  0x010480UL
@@ -52,12 +53,17 @@ typedef struct S390IPLState {
     uint64_t start_addr;
     uint64_t bios_start_addr;
     bool enforce_bios;
+    IplParameterBlock iplb;
+    bool iplb_valid;
 
     /*< public >*/
     char *kernel;
     char *initrd;
     char *cmdline;
     char *firmware;
+    uint8_t cssid;
+    uint8_t ssid;
+    uint16_t devno;
 } S390IPLState;
 
 
@@ -164,6 +170,69 @@ static Property s390_ipl_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+/*
+ * In addition to updating the iplstate, this function returns:
+ * - 0 if system was ipled with external kernel
+ * - -1 if no valid boot device was found
+ * - ccw id of the boot device otherwise
+ */
+static uint64_t s390_update_iplstate(CPUS390XState *env, S390IPLState *ipl)
+{
+    DeviceState *dev_st;
+
+    if (ipl->iplb_valid) {
+        ipl->cssid = 0;
+        ipl->ssid = 0;
+        ipl->devno = ipl->iplb.devno;
+        goto out;
+    }
+
+    if (ipl->kernel) {
+        return 0;
+    }
+
+    dev_st = get_boot_device(0);
+    if (dev_st) {
+        VirtioCcwDevice *ccw_dev = (VirtioCcwDevice *) object_dynamic_cast(
+            OBJECT(qdev_get_parent_bus(dev_st)->parent),
+                TYPE_VIRTIO_CCW_DEVICE);
+        if (ccw_dev) {
+            ipl->cssid = ccw_dev->sch->cssid;
+            ipl->ssid = ccw_dev->sch->ssid;
+            ipl->devno = ccw_dev->sch->devno;
+            goto out;
+        }
+    }
+
+    return -1;
+out:
+    return ipl->cssid << 24 | ipl->ssid << 16 | ipl->devno;
+}
+
+int s390_ipl_update_diag308(IplParameterBlock *iplb)
+{
+    S390IPLState *ipl;
+
+    ipl = S390_IPL(object_resolve_path(TYPE_S390_IPL, NULL));
+    if (ipl) {
+        ipl->iplb = *iplb;
+        ipl->iplb_valid = true;
+        return 0;
+    }
+    return -1;
+}
+
+IplParameterBlock *s390_ipl_get_iplb(void)
+{
+    S390IPLState *ipl;
+
+    ipl = S390_IPL(object_resolve_path(TYPE_S390_IPL, NULL));
+    if (!ipl || !ipl->iplb_valid) {
+        return NULL;
+    }
+    return &ipl->iplb;
+}
+
 static void s390_ipl_reset(DeviceState *dev)
 {
     S390IPLState *ipl = S390_IPL(dev);
@@ -173,21 +242,9 @@ static void s390_ipl_reset(DeviceState *dev)
     env->psw.addr = ipl->start_addr;
     env->psw.mask = IPL_PSW_MASK;
 
-    if (!ipl->kernel) {
-        /* Tell firmware, if there is a preferred boot device */
-        env->regs[7] = -1;
-        DeviceState *dev_st = get_boot_device(0);
-        if (dev_st) {
-            VirtioCcwDevice *ccw_dev = (VirtioCcwDevice *) object_dynamic_cast(
-                OBJECT(qdev_get_parent_bus(dev_st)->parent),
-                TYPE_VIRTIO_CCW_DEVICE);
-
-            if (ccw_dev) {
-                env->regs[7] = ccw_dev->sch->cssid << 24 |
-                               ccw_dev->sch->ssid << 16 |
-                               ccw_dev->sch->devno;
-            }
-        }
+    if (!ipl->kernel || ipl->iplb_valid) {
+        env->psw.addr = ipl->bios_start_addr;
+        env->regs[7] = s390_update_iplstate(env, ipl);
     }
 
     s390_cpu_set_state(CPU_STATE_OPERATING, cpu);

hw/s390x/ipl.h

@@ -0,0 +1,24 @@
+/*
+ * s390 IPL device
+ *
+ * Copyright 2015 IBM Corp.
+ * Author(s): Zhang Fan <bjfanzh@cn.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at
+ * your option) any later version. See the COPYING file in the top-level
+ * directory.
+ */
+
+#ifndef HW_S390_IPL_H
+#define HW_S390_IPL_H
+
+typedef struct IplParameterBlock {
+      uint8_t  reserved1[110];
+      uint16_t devno;
+      uint8_t  reserved2[88];
+} IplParameterBlock;
+
+int s390_ipl_update_diag308(IplParameterBlock *iplb);
+IplParameterBlock *s390_ipl_get_iplb(void);
+
+#endif

hw/s390x/s390-virtio.c

@@ -143,6 +143,8 @@ void s390_init_ipl_dev(const char *kernel_filename,
     qdev_prop_set_string(dev, "cmdline", kernel_cmdline);
     qdev_prop_set_string(dev, "firmware", firmware);
     qdev_prop_set_bit(dev, "enforce_bios", enforce_bios);
+    object_property_add_child(qdev_get_machine(), "s390-ipl",
+                              OBJECT(dev), NULL);
     qdev_init_nofail(dev);
 }
 

target-s390x/misc_helper.c

@@ -25,6 +25,7 @@
 #include <string.h>
 #include "sysemu/kvm.h"
 #include "qemu/timer.h"
+#include "exec/address-spaces.h"
 #ifdef CONFIG_KVM
 #include <linux/kvm.h>
 #endif
@@ -34,6 +35,7 @@
 #include "sysemu/cpus.h"
 #include "sysemu/sysemu.h"
 #include "hw/s390x/ebcdic.h"
+#include "hw/s390x/ipl.h"
 #endif
 
 /* #define DEBUG_HELPER */
@@ -151,12 +153,15 @@ static int load_normal_reset(S390CPU *cpu)
     return 0;
 }
 
+#define DIAG_308_RC_OK              0x0001
 #define DIAG_308_RC_NO_CONF         0x0102
 #define DIAG_308_RC_INVALID         0x0402
+
 void handle_diag_308(CPUS390XState *env, uint64_t r1, uint64_t r3)
 {
     uint64_t addr =  env->regs[r1];
     uint64_t subcode = env->regs[r3];
+    IplParameterBlock *iplb;
 
     if (env->psw.mask & PSW_MASK_PSTATE) {
         program_interrupt(env, PGM_PRIVILEGED, ILEN_LATER_INC);
@@ -180,14 +185,38 @@ void handle_diag_308(CPUS390XState *env, uint64_t r1, uint64_t r3)
             program_interrupt(env, PGM_SPECIFICATION, ILEN_LATER_INC);
             return;
         }
-        env->regs[r1+1] = DIAG_308_RC_INVALID;
+        if (!address_space_access_valid(&address_space_memory, addr,
+                                        sizeof(IplParameterBlock), false)) {
+            program_interrupt(env, PGM_ADDRESSING, ILEN_LATER_INC);
+            return;
+        }
+        iplb = g_malloc0(sizeof(struct IplParameterBlock));
+        cpu_physical_memory_read(addr, iplb, sizeof(struct IplParameterBlock));
+        if (!s390_ipl_update_diag308(iplb)) {
+            env->regs[r1 + 1] = DIAG_308_RC_OK;
+        } else {
+            env->regs[r1 + 1] = DIAG_308_RC_INVALID;
+        }
+        g_free(iplb);
         return;
     case 6:
         if ((r1 & 1) || (addr & 0x0fffULL)) {
             program_interrupt(env, PGM_SPECIFICATION, ILEN_LATER_INC);
             return;
         }
-        env->regs[r1+1] = DIAG_308_RC_NO_CONF;
+        if (!address_space_access_valid(&address_space_memory, addr,
+                                        sizeof(IplParameterBlock), true)) {
+            program_interrupt(env, PGM_ADDRESSING, ILEN_LATER_INC);
+            return;
+        }
+        iplb = s390_ipl_get_iplb();
+        if (iplb) {
+            cpu_physical_memory_write(addr, iplb,
+                                      sizeof(struct IplParameterBlock));
+            env->regs[r1 + 1] = DIAG_308_RC_OK;
+        } else {
+            env->regs[r1 + 1] = DIAG_308_RC_NO_CONF;
+        }
         return;
     default:
         hw_error("Unhandled diag308 subcode %" PRIx64, subcode);