target-i386: fix disassembly with PAE=1, PG=0

CR4.PAE=1 will not enable paging if CR0.PG=0, but the "if" chain
in x86_cpu_get_phys_page_debug says otherwise.  Check CR0.PG
before everything else.

Fixes "-d in_asm" for a code section at the beginning of OVMF.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRichard Henderson <rth@twiddle.net>
Reviewed-by: NMax Filippov <jcmvbkbc@gmail.com>

target-i386/helper.c

@@ -894,7 +894,10 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
     uint32_t page_offset;
     int page_size;
 
-    if (env->cr[4] & CR4_PAE_MASK) {
+    if (!(env->cr[0] & CR0_PG_MASK)) {
+        pte = addr & env->a20_mask;
+        page_size = 4096;
+    } else if (env->cr[4] & CR4_PAE_MASK) {
         target_ulong pdpe_addr;
         uint64_t pde, pdpe;
 
@@ -952,26 +955,21 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
     } else {
         uint32_t pde;
 
-        if (!(env->cr[0] & CR0_PG_MASK)) {
-            pte = addr;
-            page_size = 4096;
+        /* page directory entry */
+        pde_addr = ((env->cr[3] & ~0xfff) + ((addr >> 20) & 0xffc)) & env->a20_mask;
+        pde = ldl_phys(pde_addr);
+        if (!(pde & PG_PRESENT_MASK))
+            return -1;
+        if ((pde & PG_PSE_MASK) && (env->cr[4] & CR4_PSE_MASK)) {
+            pte = pde & ~0x003ff000; /* align to 4MB */
+            page_size = 4096 * 1024;
         } else {
             /* page directory entry */
-            pde_addr = ((env->cr[3] & ~0xfff) + ((addr >> 20) & 0xffc)) & env->a20_mask;
-            pde = ldl_phys(pde_addr);
-            if (!(pde & PG_PRESENT_MASK))
+            pte_addr = ((pde & ~0xfff) + ((addr >> 10) & 0xffc)) & env->a20_mask;
+            pte = ldl_phys(pte_addr);
+            if (!(pte & PG_PRESENT_MASK))
                 return -1;
-            if ((pde & PG_PSE_MASK) && (env->cr[4] & CR4_PSE_MASK)) {
-                pte = pde & ~0x003ff000; /* align to 4MB */
-                page_size = 4096 * 1024;
-            } else {
-                /* page directory entry */
-                pte_addr = ((pde & ~0xfff) + ((addr >> 10) & 0xffc)) & env->a20_mask;
-                pte = ldl_phys(pte_addr);
-                if (!(pte & PG_PRESENT_MASK))
-                    return -1;
-                page_size = 4096;
-            }
+            page_size = 4096;
         }
         pte = pte & env->a20_mask;
     }