diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 9924e66d1f..e4f703a7e6 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -173,8 +173,13 @@ struct page_collection {
 #define TB_FOR_EACH_JMP(head_tb, tb, n)                                 \
     TB_FOR_EACH_TAGGED((head_tb)->jmp_list_head, tb, n, jmp_list_next)
 
-/* In system mode we want L1_MAP to be based on ram offsets,
-   while in user mode we want it to be based on virtual addresses.  */
+/*
+ * In system mode we want L1_MAP to be based on ram offsets,
+ * while in user mode we want it to be based on virtual addresses.
+ *
+ * TODO: For user mode, see the caveat re host vs guest virtual
+ * address spaces near GUEST_ADDR_MAX.
+ */
 #if !defined(CONFIG_USER_ONLY)
 #if HOST_LONG_BITS < TARGET_PHYS_ADDR_SPACE_BITS
 # define L1_MAP_ADDR_SPACE_BITS  HOST_LONG_BITS
@@ -182,7 +187,7 @@ struct page_collection {
 # define L1_MAP_ADDR_SPACE_BITS  TARGET_PHYS_ADDR_SPACE_BITS
 #endif
 #else
-# define L1_MAP_ADDR_SPACE_BITS  TARGET_VIRT_ADDR_SPACE_BITS
+# define L1_MAP_ADDR_SPACE_BITS  MIN(HOST_LONG_BITS, TARGET_ABI_BITS)
 #endif
 
 /* Size of the L2 (and L3, etc) page tables.  */
@@ -2497,9 +2502,7 @@ void page_set_flags(target_ulong start, target_ulong end, int flags)
     /* This function should never be called with addresses outside the
        guest address space.  If this assert fires, it probably indicates
        a missing call to h2g_valid.  */
-#if TARGET_ABI_BITS > L1_MAP_ADDR_SPACE_BITS
-    assert(end <= ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS));
-#endif
+    assert(end - 1 <= GUEST_ADDR_MAX);
     assert(start < end);
     assert_memory_lock();
 
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 0895a57881..d14374bdd4 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -162,12 +162,27 @@ extern unsigned long guest_base;
 extern bool have_guest_base;
 extern unsigned long reserved_va;
 
-#if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
-#define GUEST_ADDR_MAX (~0ul)
+/*
+ * Limit the guest addresses as best we can.
+ *
+ * When not using -R reserved_va, we cannot really limit the guest
+ * to less address space than the host.  For 32-bit guests, this
+ * acts as a sanity check that we're not giving the guest an address
+ * that it cannot even represent.  For 64-bit guests... the address
+ * might not be what the real kernel would give, but it is at least
+ * representable in the guest.
+ *
+ * TODO: Improve address allocation to avoid this problem, and to
+ * avoid setting bits at the top of guest addresses that might need
+ * to be used for tags.
+ */
+#if MIN(TARGET_VIRT_ADDR_SPACE_BITS, TARGET_ABI_BITS) <= 32
+# define GUEST_ADDR_MAX_  UINT32_MAX
 #else
-#define GUEST_ADDR_MAX (reserved_va ? reserved_va - 1 : \
-                                    (1ul << TARGET_VIRT_ADDR_SPACE_BITS) - 1)
+# define GUEST_ADDR_MAX_  (~0ul)
 #endif
+#define GUEST_ADDR_MAX    (reserved_va ? reserved_va - 1 : GUEST_ADDR_MAX_)
+
 #else
 
 #include "exec/hwaddr.h"
diff --git a/target/alpha/cpu-param.h b/target/alpha/cpu-param.h
index 692aee27ca..1153992e42 100644
--- a/target/alpha/cpu-param.h
+++ b/target/alpha/cpu-param.h
@@ -10,22 +10,11 @@
 
 #define TARGET_LONG_BITS 64
 #define TARGET_PAGE_BITS 13
-#ifdef CONFIG_USER_ONLY
-/*
- * ??? The kernel likes to give addresses in high memory.  If the host has
- * more virtual address space than the guest, this can lead to impossible
- * allocations.  Honor the long-standing assumption that only kernel addrs
- * are negative, but otherwise allow allocations anywhere.  This could lead
- * to tricky emulation problems for programs doing tagged addressing, but
- * that's far fewer than encounter the impossible allocation problem.
- */
-#define TARGET_PHYS_ADDR_SPACE_BITS  63
-#define TARGET_VIRT_ADDR_SPACE_BITS  63
-#else
+
 /* ??? EV4 has 34 phys addr bits, EV5 has 40, EV6 has 44.  */
 #define TARGET_PHYS_ADDR_SPACE_BITS  44
 #define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
-#endif
+
 #define NB_MMU_MODES 3
 
 #endif