1 files changed, 45 insertions, 3 deletions

diff --git a/page-vary-target.c b/page-vary-target.c
index 3f81144..49a32b4 100644
--- a/page-vary-target.c
+++ b/page-vary-target.c
@@ -21,12 +21,47 @@
 
 #include "qemu/osdep.h"
 #include "exec/page-vary.h"
-#include "exec/exec-all.h"
+#include "exec/target_page.h"
 
-bool set_preferred_target_page_bits(int bits)
+
+/*
+ * For system mode, the minimum comes from the number of bits
+ * required for maximum alignment (6) and the number of bits
+ * required for TLB_FLAGS_MASK (3).
+ *
+ * For user mode, TARGET_PAGE_BITS_VARY is a hack to allow the target
+ * page size to match the host page size.  Mostly, this reduces the
+ * ordinary target page size to run on a host with 4KiB pages (i.e. x86).
+ * There is no true minimum required by the implementation, but keep the
+ * same minimum as for system mode for sanity.
+ * See linux-user/mmap.c, mmap_h_lt_g and mmap_h_gt_g.
+ */
+#define TARGET_PAGE_BITS_MIN 9
+
+#ifndef TARGET_PAGE_BITS_VARY
+QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS < TARGET_PAGE_BITS_MIN);
+#endif
+
+#ifndef CONFIG_USER_ONLY
+#include "exec/tlb-flags.h"
+
+QEMU_BUILD_BUG_ON(TLB_FLAGS_MASK & ((1u < TARGET_PAGE_BITS_MIN) - 1));
+
+int migration_legacy_page_bits(void)
 {
 #ifdef TARGET_PAGE_BITS_VARY
+    QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS_LEGACY < TARGET_PAGE_BITS_MIN);
+    return TARGET_PAGE_BITS_LEGACY;
+#else
+    return TARGET_PAGE_BITS;
+#endif
+}
+#endif
+
+bool set_preferred_target_page_bits(int bits)
+{
     assert(bits >= TARGET_PAGE_BITS_MIN);
+#ifdef TARGET_PAGE_BITS_VARY
     return set_preferred_target_page_bits_common(bits);
 #else
     return true;
@@ -35,5 +70,12 @@ bool set_preferred_target_page_bits(int bits)
 
 void finalize_target_page_bits(void)
 {
-    finalize_target_page_bits_common(TARGET_PAGE_BITS_MIN);
+#ifndef TARGET_PAGE_BITS_VARY
+    finalize_target_page_bits_common(TARGET_PAGE_BITS);
+#elif defined(CONFIG_USER_ONLY)
+    assert(target_page.bits != 0);
+    finalize_target_page_bits_common(target_page.bits);
+#else
+    finalize_target_page_bits_common(TARGET_PAGE_BITS_LEGACY);
+#endif
 }