Re: [PATCH v5 1/2] target/s390x: Implement the MVPG condition-code-option bit

[David Hildenbrand]

On 11.03.21 18:52, Richard Henderson wrote:
On 3/11/21 10:17 AM, David Hildenbrand wrote:
+#if !defined(CONFIG_USER_ONLY)
+    /*
+     * For !CONFIG_USER_ONLY, we cannot rely on TLB_INVALID_MASK or haddr==NULL
+     * to detect if there was an exception during tlb_fill().
+     */
+    env->tlb_fill_exc = 0;
+#endif
+    flags = probe_access_flags(env, vaddr1, access_type, mmu_idx,
+                               nofault, &haddr1, ra);
+#if !defined(CONFIG_USER_ONLY)
+    if (env->tlb_fill_exc) {
+        return env->tlb_fill_exc;
+    }
+#else
+    if (!haddr1) {
+        env->__excp_addr = vaddr1;
+        return PGM_ADDRESSING;
+    }
+#endif

The assumption of PGM_ADDRESSING is incorrect here -- it could still be
PGM_PROTECTION, depending on how the page is mapped.


Interesting, I was only looking at the s390x tlb_fill() implementation. 
But I assume these checks are performed in common code.

I guess this should be done like

#ifdef CONFIG_USER_ONLY
      flags = page_get_flags(vaddr1);
      if (!flags & (access_type == MMU_DATA_LOAD
                    ? PAGE_READ : PAGE_WRITE)) {
          env->__excp_addr = vaddr1;
          if (nofault) {
              return (flags & PAGE_VALID
                  ? PGM_PROTECTION : PGM_ADDRESSING);
          }
          raise exception.
      }
      haddr1 = g2h(vaddr1);
#else
      env->tlb_fill_exc = 0;
      flags = probe_access_flags(...);
      if (env->tlb_fill_exc) {
          return env->tlb_fill_exc;
      }
#endif

which is pretty ugly, but no worse than what you have above.

Thanks, maybe I can factor that out in a nice way. I guess we could do 
the access via probe_access_flags() and only on error do the 
page_get_flags()?


--
Thanks,

David / dhildenb