[PULL 42/47] target/ppc: Fix 440 tlbwe TLB invalidation gaps

[Nicholas Piggin]

The 440 tlbwe (write entry) instruction misses several cases that must
flush the TCG TLB:

- If the new size is smaller than the existing size, the EA no longer
  covered should be flushed. This looks like an inverted inequality
  test.
- If the TLB PID changes.
- If the TLB attr bit 0 (translation address space) changes.
- If low prot (access control) bits change.

Fix this by removing tricks to avoid TLB flushes, and just invalidate
the TLB if any valid entry is being changed, similarly to 4xx.
Optimisations will be introduced in subsequent changes.

Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Acked-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/mmu_helper.c | 35 ++++++++++-------------------------
 1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/target/ppc/mmu_helper.c b/target/ppc/mmu_helper.c
index f87d35379a..c140f3c96d 100644
--- a/target/ppc/mmu_helper.c
+++ b/target/ppc/mmu_helper.c
@@ -855,49 +855,34 @@ void helper_440_tlbwe(CPUPPCState *env, uint32_t word, 
target_ulong entry,
                       target_ulong value)
 {
     ppcemb_tlb_t *tlb;
-    target_ulong EPN, RPN, size;
-    int do_flush_tlbs;
 
     qemu_log_mask(CPU_LOG_MMU, "%s word %d entry %d value " TARGET_FMT_lx "\n",
                   __func__, word, (int)entry, value);
-    do_flush_tlbs = 0;
     entry &= 0x3F;
     tlb = &env->tlb.tlbe[entry];
+
+    /* Invalidate previous TLB (if it's valid) */
+    if (tlb->prot & PAGE_VALID) {
+        tlb_flush(env_cpu(env));
+    }
+
     switch (word) {
     default:
         /* Just here to please gcc */
     case 0:
-        EPN = value & 0xFFFFFC00;
-        if ((tlb->prot & PAGE_VALID) && EPN != tlb->EPN) {
-            do_flush_tlbs = 1;
-        }
-        tlb->EPN = EPN;
-        size = booke_tlb_to_page_size((value >> 4) & 0xF);
-        if ((tlb->prot & PAGE_VALID) && tlb->size < size) {
-            do_flush_tlbs = 1;
-        }
-        tlb->size = size;
+        tlb->EPN = value & 0xFFFFFC00;
+        tlb->size = booke_tlb_to_page_size((value >> 4) & 0xF);
         tlb->attr &= ~0x1;
         tlb->attr |= (value >> 8) & 1;
         if (value & 0x200) {
             tlb->prot |= PAGE_VALID;
         } else {
-            if (tlb->prot & PAGE_VALID) {
-                tlb->prot &= ~PAGE_VALID;
-                do_flush_tlbs = 1;
-            }
+            tlb->prot &= ~PAGE_VALID;
         }
         tlb->PID = env->spr[SPR_440_MMUCR] & 0x000000FF;
-        if (do_flush_tlbs) {
-            tlb_flush(env_cpu(env));
-        }
         break;
     case 1:
-        RPN = value & 0xFFFFFC0F;
-        if ((tlb->prot & PAGE_VALID) && tlb->RPN != RPN) {
-            tlb_flush(env_cpu(env));
-        }
-        tlb->RPN = RPN;
+        tlb->RPN = value & 0xFFFFFC0F;
         break;
     case 2:
         tlb->attr = (tlb->attr & 0x1) | (value & 0x0000FF00);
-- 
2.42.0