Merge remote-tracking branch 'remotes/borntraeger/tags/s390x-20190930' into staging

- do not abuse memory_region_allocate_system_memory and split the memory
  according to KVM memslots in KVM code instead (Paolo, Igor)
- change splitting to split at 4TB (Christian)
- do not claim s390 (31bit) support in configure (Thomas)
- sclp error checking (Janosch, Claudio)
- new s390 pci maintainer (Matt, Collin)
- fix s390 pci (again) (Matt)

# gpg: Signature made Mon 30 Sep 2019 12:52:51 BST
# gpg:                using RSA key 117BBC80B5A61C7C
# gpg: Good signature from "Christian Borntraeger (IBM) <borntraeger@de.ibm.com>" [full]
# Primary key fingerprint: F922 9381 A334 08F9 DBAB  FBCA 117B BC80 B5A6 1C7C

* remotes/borntraeger/tags/s390x-20190930:
  s390/kvm: split kvm mem slots at 4TB
  s390: do not call memory_region_allocate_system_memory() multiple times
  kvm: split too big memory section on several memslots
  kvm: clear dirty bitmaps from all overlapping memslots
  kvm: extract kvm_log_clear_one_slot
  configure: Remove s390 (31-bit mode) from the list of supported CPUs
  s390x: sclp: Report insufficient SCCB length
  s390x: sclp: fix error handling for oversize control blocks
  s390x: sclp: boundary check
  s390x: sclp: refactor invalid command check
  s390: PCI: fix IOMMU region init
  MAINTAINERS: Update S390 PCI Maintainer

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

9 files changed, 203 insertions, 128 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index bd7ee23..21264ea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1206,7 +1206,7 @@ T: git https://github.com/borntraeger/qemu.git s390-next
 L: qemu-s390x@nongnu.org
 
 S390 PCI
-M: Collin Walling <walling@linux.ibm.com>
+M: Matthew Rosato <mjrosato@linux.ibm.com>
 S: Supported
 F: hw/s390x/s390-pci*
 L: qemu-s390x@nongnu.org
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index b09bad0..aabe097 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -140,6 +140,7 @@ bool kvm_direct_msi_allowed;
 bool kvm_ioeventfd_any_length_allowed;
 bool kvm_msi_use_devid;
 static bool kvm_immediate_exit;
+static hwaddr kvm_max_slot_size = ~0;
 
 static const KVMCapabilityInfo kvm_required_capabilites[] = {
     KVM_CAP_INFO(USER_MEMORY),
@@ -437,7 +438,7 @@ static int kvm_slot_update_flags(KVMMemoryListener *kml, KVMSlot *mem,
 static int kvm_section_update_flags(KVMMemoryListener *kml,
                                     MemoryRegionSection *section)
 {
-    hwaddr start_addr, size;
+    hwaddr start_addr, size, slot_size;
     KVMSlot *mem;
     int ret = 0;
 
@@ -448,13 +449,18 @@ static int kvm_section_update_flags(KVMMemoryListener *kml,
 
     kvm_slots_lock(kml);
 
-    mem = kvm_lookup_matching_slot(kml, start_addr, size);
-    if (!mem) {
-        /* We don't have a slot if we want to trap every access. */
-        goto out;
-    }
+    while (size && !ret) {
+        slot_size = MIN(kvm_max_slot_size, size);
+        mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
+        if (!mem) {
+            /* We don't have a slot if we want to trap every access. */
+            goto out;
+        }
 
-    ret = kvm_slot_update_flags(kml, mem, section->mr);
+        ret = kvm_slot_update_flags(kml, mem, section->mr);
+        start_addr += slot_size;
+        size -= slot_size;
+    }
 
 out:
     kvm_slots_unlock(kml);
@@ -527,11 +533,15 @@ static int kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
     struct kvm_dirty_log d = {};
     KVMSlot *mem;
     hwaddr start_addr, size;
+    hwaddr slot_size, slot_offset = 0;
     int ret = 0;
 
     size = kvm_align_section(section, &start_addr);
-    if (size) {
-        mem = kvm_lookup_matching_slot(kml, start_addr, size);
+    while (size) {
+        MemoryRegionSection subsection = *section;
+
+        slot_size = MIN(kvm_max_slot_size, size);
+        mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
         if (!mem) {
             /* We don't have a slot if we want to trap every access. */
             goto out;
@@ -549,11 +559,11 @@ static int kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
          * So for now, let's align to 64 instead of HOST_LONG_BITS here, in
          * a hope that sizeof(long) won't become >8 any time soon.
          */
-        size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
-                     /*HOST_LONG_BITS*/ 64) / 8;
         if (!mem->dirty_bmap) {
+            hwaddr bitmap_size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
+                                        /*HOST_LONG_BITS*/ 64) / 8;
             /* Allocate on the first log_sync, once and for all */
-            mem->dirty_bmap = g_malloc0(size);
+            mem->dirty_bmap = g_malloc0(bitmap_size);
         }
 
         d.dirty_bitmap = mem->dirty_bmap;
@@ -564,7 +574,13 @@ static int kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
             goto out;
         }
 
-        kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
+        subsection.offset_within_region += slot_offset;
+        subsection.size = int128_make64(slot_size);
+        kvm_get_dirty_pages_log_range(&subsection, d.dirty_bitmap);
+
+        slot_offset += slot_size;
+        start_addr += slot_size;
+        size -= slot_size;
     }
 out:
     return ret;
@@ -575,63 +591,22 @@ out:
 #define KVM_CLEAR_LOG_ALIGN  (qemu_real_host_page_size << KVM_CLEAR_LOG_SHIFT)
 #define KVM_CLEAR_LOG_MASK   (-KVM_CLEAR_LOG_ALIGN)
 
-/**
- * kvm_physical_log_clear - Clear the kernel's dirty bitmap for range
- *
- * NOTE: this will be a no-op if we haven't enabled manual dirty log
- * protection in the host kernel because in that case this operation
- * will be done within log_sync().
- *
- * @kml:     the kvm memory listener
- * @section: the memory range to clear dirty bitmap
- */
-static int kvm_physical_log_clear(KVMMemoryListener *kml,
-                                  MemoryRegionSection *section)
+static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
+                                  uint64_t size)
 {
     KVMState *s = kvm_state;
+    uint64_t end, bmap_start, start_delta, bmap_npages;
     struct kvm_clear_dirty_log d;
-    uint64_t start, end, bmap_start, start_delta, bmap_npages, size;
     unsigned long *bmap_clear = NULL, psize = qemu_real_host_page_size;
-    KVMSlot *mem = NULL;
-    int ret, i;
-
-    if (!s->manual_dirty_log_protect) {
-        /* No need to do explicit clear */
-        return 0;
-    }
-
-    start = section->offset_within_address_space;
-    size = int128_get64(section->size);
-
-    if (!size) {
-        /* Nothing more we can do... */
-        return 0;
-    }
-
-    kvm_slots_lock(kml);
-
-    /* Find any possible slot that covers the section */
-    for (i = 0; i < s->nr_slots; i++) {
-        mem = &kml->slots[i];
-        if (mem->start_addr <= start &&
-            start + size <= mem->start_addr + mem->memory_size) {
-            break;
-        }
-    }
-
-    /*
-     * We should always find one memslot until this point, otherwise
-     * there could be something wrong from the upper layer
-     */
-    assert(mem && i != s->nr_slots);
+    int ret;
 
     /*
      * We need to extend either the start or the size or both to
      * satisfy the KVM interface requirement.  Firstly, do the start
      * page alignment on 64 host pages
      */
-    bmap_start = (start - mem->start_addr) & KVM_CLEAR_LOG_MASK;
-    start_delta = start - mem->start_addr - bmap_start;
+    bmap_start = start & KVM_CLEAR_LOG_MASK;
+    start_delta = start - bmap_start;
     bmap_start /= psize;
 
     /*
@@ -694,7 +669,7 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
     /* It should never overflow.  If it happens, say something */
     assert(bmap_npages <= UINT32_MAX);
     d.num_pages = bmap_npages;
-    d.slot = mem->slot | (kml->as_id << 16);
+    d.slot = mem->slot | (as_id << 16);
 
     if (kvm_vm_ioctl(s, KVM_CLEAR_DIRTY_LOG, &d) == -1) {
         ret = -errno;
@@ -717,6 +692,66 @@ static int kvm_physical_log_clear(KVMMemoryListener *kml,
                  size / psize);
     /* This handles the NULL case well */
     g_free(bmap_clear);
+    return ret;
+}
+
+
+/**
+ * kvm_physical_log_clear - Clear the kernel's dirty bitmap for range
+ *
+ * NOTE: this will be a no-op if we haven't enabled manual dirty log
+ * protection in the host kernel because in that case this operation
+ * will be done within log_sync().
+ *
+ * @kml:     the kvm memory listener
+ * @section: the memory range to clear dirty bitmap
+ */
+static int kvm_physical_log_clear(KVMMemoryListener *kml,
+                                  MemoryRegionSection *section)
+{
+    KVMState *s = kvm_state;
+    uint64_t start, size, offset, count;
+    KVMSlot *mem;
+    int ret, i;
+
+    if (!s->manual_dirty_log_protect) {
+        /* No need to do explicit clear */
+        return 0;
+    }
+
+    start = section->offset_within_address_space;
+    size = int128_get64(section->size);
+
+    if (!size) {
+        /* Nothing more we can do... */
+        return 0;
+    }
+
+    kvm_slots_lock(kml);
+
+    for (i = 0; i < s->nr_slots; i++) {
+        mem = &kml->slots[i];
+        /* Discard slots that are empty or do not overlap the section */
+        if (!mem->memory_size ||
+            mem->start_addr > start + size - 1 ||
+            start > mem->start_addr + mem->memory_size - 1) {
+            continue;
+        }
+
+        if (start >= mem->start_addr) {
+            /* The slot starts before section or is aligned to it.  */
+            offset = start - mem->start_addr;
+            count = MIN(mem->memory_size - offset, size);
+        } else {
+            /* The slot starts after section.  */
+            offset = 0;
+            count = MIN(mem->memory_size, size - (mem->start_addr - start));
+        }
+        ret = kvm_log_clear_one_slot(mem, kml->as_id, offset, count);
+        if (ret < 0) {
+            break;
+        }
+    }
 
     kvm_slots_unlock(kml);
 
@@ -953,6 +988,14 @@ kvm_check_extension_list(KVMState *s, const KVMCapabilityInfo *list)
     return NULL;
 }
 
+void kvm_set_max_memslot_size(hwaddr max_slot_size)
+{
+    g_assert(
+        ROUND_UP(max_slot_size, qemu_real_host_page_size) == max_slot_size
+    );
+    kvm_max_slot_size = max_slot_size;
+}
+
 static void kvm_set_phys_mem(KVMMemoryListener *kml,
                              MemoryRegionSection *section, bool add)
 {
@@ -960,7 +1003,7 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
     int err;
     MemoryRegion *mr = section->mr;
     bool writeable = !mr->readonly && !mr->rom_device;
-    hwaddr start_addr, size;
+    hwaddr start_addr, size, slot_size;
     void *ram;
 
     if (!memory_region_is_ram(mr)) {
@@ -985,41 +1028,52 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
     kvm_slots_lock(kml);
 
     if (!add) {
-        mem = kvm_lookup_matching_slot(kml, start_addr, size);
-        if (!mem) {
-            goto out;
-        }
-        if (mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
-            kvm_physical_sync_dirty_bitmap(kml, section);
-        }
+        do {
+            slot_size = MIN(kvm_max_slot_size, size);
+            mem = kvm_lookup_matching_slot(kml, start_addr, slot_size);
+            if (!mem) {
+                goto out;
+            }
+            if (mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+                kvm_physical_sync_dirty_bitmap(kml, section);
+            }
 
-        /* unregister the slot */
-        g_free(mem->dirty_bmap);
-        mem->dirty_bmap = NULL;
-        mem->memory_size = 0;
-        mem->flags = 0;
-        err = kvm_set_user_memory_region(kml, mem, false);
-        if (err) {
-            fprintf(stderr, "%s: error unregistering slot: %s\n",
-                    __func__, strerror(-err));
-            abort();
-        }
+            /* unregister the slot */
+            g_free(mem->dirty_bmap);
+            mem->dirty_bmap = NULL;
+            mem->memory_size = 0;
+            mem->flags = 0;
+            err = kvm_set_user_memory_region(kml, mem, false);
+            if (err) {
+                fprintf(stderr, "%s: error unregistering slot: %s\n",
+                        __func__, strerror(-err));
+                abort();
+            }
+            start_addr += slot_size;
+            size -= slot_size;
+        } while (size);
         goto out;
     }
 
     /* register the new slot */
-    mem = kvm_alloc_slot(kml);
-    mem->memory_size = size;
-    mem->start_addr = start_addr;
-    mem->ram = ram;
-    mem->flags = kvm_mem_flags(mr);
-
-    err = kvm_set_user_memory_region(kml, mem, true);
-    if (err) {
-        fprintf(stderr, "%s: error registering slot: %s\n", __func__,
-                strerror(-err));
-        abort();
-    }
+    do {
+        slot_size = MIN(kvm_max_slot_size, size);
+        mem = kvm_alloc_slot(kml);
+        mem->memory_size = slot_size;
+        mem->start_addr = start_addr;
+        mem->ram = ram;
+        mem->flags = kvm_mem_flags(mr);
+
+        err = kvm_set_user_memory_region(kml, mem, true);
+        if (err) {
+            fprintf(stderr, "%s: error registering slot: %s\n", __func__,
+                    strerror(-err));
+            abort();
+        }
+        start_addr += slot_size;
+        ram += slot_size;
+        size -= slot_size;
+    } while (size);
 
 out:
     kvm_slots_unlock(kml);
@@ -2859,6 +2913,7 @@ static bool kvm_accel_has_memory(MachineState *ms, AddressSpace *as,
 
     for (i = 0; i < kvm->nr_as; ++i) {
         if (kvm->as[i].as == as && kvm->as[i].ml) {
+            size = MIN(kvm_max_slot_size, size);
             return NULL != kvm_lookup_matching_slot(kvm->as[i].ml,
                                                     start_addr, size);
         }
diff --git a/configure b/configure
index 542f6ae..8f8446f 100755
--- a/configure
+++ b/configure
@@ -728,7 +728,7 @@ ARCH=
 # Normalise host CPU name and set ARCH.
 # Note that this case should only have supported host CPUs, not guests.
 case "$cpu" in
-  ppc|ppc64|s390|s390x|sparc64|x32|riscv32|riscv64)
+  ppc|ppc64|s390x|sparc64|x32|riscv32|riscv64)
     supported_cpu="yes"
   ;;
   ppc64le)
diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
index 797ecbb..6620569 100644
--- a/hw/s390x/event-facility.c
+++ b/hw/s390x/event-facility.c
@@ -377,9 +377,6 @@ static void command_handler(SCLPEventFacility *ef, SCCB *sccb, uint64_t code)
     case SCLP_CMD_WRITE_EVENT_MASK:
         write_event_mask(ef, sccb);
         break;
-    default:
-        sccb->h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
-        break;
     }
 }
 
diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 963a41c..2d2f4a7 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -695,10 +695,15 @@ static const MemoryRegionOps s390_msi_ctrl_ops = {
 
 void s390_pci_iommu_enable(S390PCIIOMMU *iommu)
 {
+    /*
+     * The iommu region is initialized against a 0-mapped address space,
+     * so the smallest IOMMU region we can define runs from 0 to the end
+     * of the PCI address space.
+     */
     char *name = g_strdup_printf("iommu-s390-%04x", iommu->pbdev->uid);
     memory_region_init_iommu(&iommu->iommu_mr, sizeof(iommu->iommu_mr),
                              TYPE_S390_IOMMU_MEMORY_REGION, OBJECT(&iommu->mr),
-                             name, iommu->pal - iommu->pba + 1);
+                             name, iommu->pal + 1);
     iommu->enabled = true;
     memory_region_add_subregion(&iommu->mr, 0, MEMORY_REGION(&iommu->iommu_mr));
     g_free(name);
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 8bfb668..18ad279 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -154,39 +154,15 @@ static void virtio_ccw_register_hcalls(void)
                                    virtio_ccw_hcall_early_printk);
 }
 
-/*
- * KVM does only support memory slots up to KVM_MEM_MAX_NR_PAGES pages
- * as the dirty bitmap must be managed by bitops that take an int as
- * position indicator. If we have a guest beyond that we will split off
- * new subregions. The split must happen on a segment boundary (1MB).
- */
-#define KVM_MEM_MAX_NR_PAGES ((1ULL << 31) - 1)
-#define SEG_MSK (~0xfffffULL)
-#define KVM_SLOT_MAX_BYTES ((KVM_MEM_MAX_NR_PAGES * TARGET_PAGE_SIZE) & SEG_MSK)
 static void s390_memory_init(ram_addr_t mem_size)
 {
     MemoryRegion *sysmem = get_system_memory();
-    ram_addr_t chunk, offset = 0;
-    unsigned int number = 0;
+    MemoryRegion *ram = g_new(MemoryRegion, 1);
     Error *local_err = NULL;
-    gchar *name;
 
     /* allocate RAM for core */
-    name = g_strdup_printf("s390.ram");
-    while (mem_size) {
-        MemoryRegion *ram = g_new(MemoryRegion, 1);
-        uint64_t size = mem_size;
-
-        /* KVM does not allow memslots >= 8 TB */
-        chunk = MIN(size, KVM_SLOT_MAX_BYTES);
-        memory_region_allocate_system_memory(ram, NULL, name, chunk);
-        memory_region_add_subregion(sysmem, offset, ram);
-        mem_size -= chunk;
-        offset += chunk;
-        g_free(name);
-        name = g_strdup_printf("s390.ram.%u", ++number);
-    }
-    g_free(name);
+    memory_region_allocate_system_memory(ram, NULL, "s390.ram", mem_size);
+    memory_region_add_subregion(sysmem, 0, ram);
 
     /*
      * Configure the maximum page size. As no memory devices were created
diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index fac7c3b..f57ce7b 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -68,6 +68,12 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
 
     read_info->ibc_val = cpu_to_be32(s390_get_ibc_val());
 
+    if (be16_to_cpu(sccb->h.length) <
+            (sizeof(ReadInfo) + cpu_count * sizeof(CPUEntry))) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
+        return;
+    }
+
     /* Configuration Characteristic (Extension) */
     s390_get_feat_block(S390_FEAT_TYPE_SCLP_CONF_CHAR,
                          read_info->conf_char);
@@ -118,6 +124,12 @@ static void sclp_read_cpu_info(SCLPDevice *sclp, SCCB *sccb)
     cpu_info->offset_configured = cpu_to_be16(offsetof(ReadCpuInfo, entries));
     cpu_info->nr_standby = cpu_to_be16(0);
 
+    if (be16_to_cpu(sccb->h.length) <
+            (sizeof(ReadCpuInfo) + cpu_count * sizeof(CPUEntry))) {
+        sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
+        return;
+    }
+
     /* The standby offset is 16-byte for each CPU */
     cpu_info->offset_standby = cpu_to_be16(cpu_info->offset_configured
         + cpu_info->nr_configured*sizeof(CPUEntry));
@@ -213,14 +225,33 @@ int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
     cpu_physical_memory_read(sccb, &work_sccb, sccb_len);
 
     /* Valid sccb sizes */
-    if (be16_to_cpu(work_sccb.h.length) < sizeof(SCCBHeader) ||
-        be16_to_cpu(work_sccb.h.length) > SCCB_SIZE) {
+    if (be16_to_cpu(work_sccb.h.length) < sizeof(SCCBHeader)) {
         r = -PGM_SPECIFICATION;
         goto out;
     }
 
-    sclp_c->execute(sclp, &work_sccb, code);
+    switch (code & SCLP_CMD_CODE_MASK) {
+    case SCLP_CMDW_READ_SCP_INFO:
+    case SCLP_CMDW_READ_SCP_INFO_FORCED:
+    case SCLP_CMDW_READ_CPU_INFO:
+    case SCLP_CMDW_CONFIGURE_IOA:
+    case SCLP_CMDW_DECONFIGURE_IOA:
+    case SCLP_CMD_READ_EVENT_DATA:
+    case SCLP_CMD_WRITE_EVENT_DATA:
+    case SCLP_CMD_WRITE_EVENT_MASK:
+        break;
+    default:
+        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_INVALID_SCLP_COMMAND);
+        goto out_write;
+    }
+
+    if ((sccb + be16_to_cpu(work_sccb.h.length)) > ((sccb & PAGE_MASK) + PAGE_SIZE)) {
+        work_sccb.h.response_code = cpu_to_be16(SCLP_RC_SCCB_BOUNDARY_VIOLATION);
+        goto out_write;
+    }
 
+    sclp_c->execute(sclp, &work_sccb, code);
+out_write:
     cpu_physical_memory_write(sccb, &work_sccb,
                               be16_to_cpu(work_sccb.h.length));
 
diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
index 72b2d1b..ac2d1f8 100644
--- a/include/sysemu/kvm_int.h
+++ b/include/sysemu/kvm_int.h
@@ -41,4 +41,5 @@ typedef struct KVMMemoryListener {
 void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml,
                                   AddressSpace *as, int as_id);
 
+void kvm_set_max_memslot_size(hwaddr max_slot_size);
 #endif
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 97a662a..c24c869 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -28,6 +28,7 @@
 #include "cpu.h"
 #include "internal.h"
 #include "kvm_s390x.h"
+#include "sysemu/kvm_int.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/timer.h"
@@ -122,6 +123,14 @@
  */
 #define VCPU_IRQ_BUF_SIZE(max_cpus) (sizeof(struct kvm_s390_irq) * \
                                      (max_cpus + NR_LOCAL_IRQS))
+/*
+ * KVM does only support memory slots up to KVM_MEM_MAX_NR_PAGES pages
+ * as the dirty bitmap must be managed by bitops that take an int as
+ * position indicator. This would end at an unaligned  address
+ * (0x7fffff00000). As future variants might provide larger pages
+ * and to make all addresses properly aligned, let us split at 4TB.
+ */
+#define KVM_SLOT_MAX_BYTES (4UL * TiB)
 
 static CPUWatchpoint hw_watchpoint;
 /*
@@ -355,6 +364,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
      */
     /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */
 
+    kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
     return 0;
 }