target/ppc: 4xx don't flush TLB for a newly written software TLB entry

BookE software TLB is implemented by flushing old translations from the
relevant TCG TLB whenever software TLB entries change. This means a new
software TLB entry should not have any corresponding cached TCG TLB
translations, so there is nothing to flush. The exception is multiple
software TLBs that cover the same address and address space, but that is
a programming error and results in undefined behaviour, and flushing
does not give an obviously better outcome in that case either.

Remove the unnecessary flush of a newly written software TLB entry.

Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Acked-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

diff --git a/target/ppc/mmu_helper.c b/target/ppc/mmu_helper.c
index 949ae87f4fd4948520d9c08cdd14c070addb45b5..68632bf54ec82351b4065306a6552ca1264fe78a 100644 (file)
--- a/target/ppc/mmu_helper.c
+++ b/target/ppc/mmu_helper.c
@@ -808,13 +808,6 @@ void helper_4xx_tlbwe_hi(CPUPPCState *env, target_ulong entry,
                   tlb->prot & PAGE_WRITE ? 'w' : '-',
                   tlb->prot & PAGE_EXEC ? 'x' : '-',
                   tlb->prot & PAGE_VALID ? 'v' : '-', (int)tlb->PID);
-    /* Invalidate new TLB (if valid) */
-    if (tlb->prot & PAGE_VALID) {
-        qemu_log_mask(CPU_LOG_MMU, "%s: invalidate TLB %d start "
-                      TARGET_FMT_lx " end " TARGET_FMT_lx "\n", __func__,
-                      (int)entry, tlb->EPN, tlb->EPN + tlb->size);
-        ppcemb_tlb_flush(cs, tlb);
-    }
 }
 
 void helper_4xx_tlbwe_lo(CPUPPCState *env, target_ulong entry,