target/loongarch: Update TLB index selection method

With function helper_tlbfill(), since there is no suitable TLB entry,
new TLB will be added and flush one old TLB entry. The old TLB entry
index is selected randomly now, instead it can be optimized as
following:
  1. invalid TLB entry can be selected at first.
  2. TLB entry with other ASID can be selected secondly
  3. random method is used by last.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/target/loongarch/tcg/tlb_helper.c b/target/loongarch/tcg/tlb_helper.c
index 88dba9eb3ea44052a4c06edc8ba9acd6f6aa6188..b46621f203ce744faa7de0a7ef887fa79e1aae30 100644 (file)
--- a/target/loongarch/tcg/tlb_helper.c
+++ b/target/loongarch/tcg/tlb_helper.c
@@ -336,8 +336,11 @@ void helper_tlbwr(CPULoongArchState *env)
 void helper_tlbfill(CPULoongArchState *env)
 {
     uint64_t address, entryhi;
-    int index, set, stlb_idx;
+    int index, set, i, stlb_idx;
     uint16_t pagesize, stlb_ps;
+    uint16_t asid, tlb_asid;
+    LoongArchTLB *tlb;
+    uint8_t tlb_e;
 
     if (FIELD_EX64(env->CSR_TLBRERA, CSR_TLBRERA, ISTLBR)) {
         entryhi = env->CSR_TLBREHI;
@@ -351,20 +354,52 @@ void helper_tlbfill(CPULoongArchState *env)
 
     /* Validity of stlb_ps is checked in helper_csrwr_stlbps() */
     stlb_ps = FIELD_EX64(env->CSR_STLBPS, CSR_STLBPS, PS);
+    asid = FIELD_EX64(env->CSR_ASID, CSR_ASID, ASID);
     if (pagesize == stlb_ps) {
         /* Only write into STLB bits [47:13] */
         address = entryhi & ~MAKE_64BIT_MASK(0, R_CSR_TLBEHI_64_VPPN_SHIFT);
-
-        /* Choose one set ramdomly */
-        set = get_random_tlb(0, 7);
-
-        /* Index in one set */
+        set = -1;
         stlb_idx = (address >> (stlb_ps + 1)) & 0xff; /* [0,255] */
+        for (i = 0; i < 8; ++i) {
+            tlb = &env->tlb[i * 256 + stlb_idx];
+            tlb_e = FIELD_EX64(tlb->tlb_misc, TLB_MISC, E);
+            if (!tlb_e) {
+                set = i;
+                break;
+            }
+
+            tlb_asid = FIELD_EX64(tlb->tlb_misc, TLB_MISC, ASID);
+            if (asid != tlb_asid) {
+                set = i;
+            }
+        }
 
+        /* Choose one set randomly */
+        if (set < 0) {
+            set = get_random_tlb(0, 7);
+        }
         index = set * 256 + stlb_idx;
     } else {
         /* Only write into MTLB */
-        index = get_random_tlb(LOONGARCH_STLB, LOONGARCH_TLB_MAX - 1);
+        index = -1;
+        for (i = LOONGARCH_STLB; i < LOONGARCH_TLB_MAX; i++) {
+            tlb = &env->tlb[i];
+            tlb_e = FIELD_EX64(tlb->tlb_misc, TLB_MISC, E);
+
+            if (!tlb_e) {
+                index = i;
+                break;
+            }
+
+            tlb_asid = FIELD_EX64(tlb->tlb_misc, TLB_MISC, ASID);
+            if (asid != tlb_asid) {
+                index = i;
+            }
+        }
+
+        if (index < 0) {
+            index = get_random_tlb(LOONGARCH_STLB, LOONGARCH_TLB_MAX - 1);
+        }
     }
 
     invalidate_tlb(env, index);