[PATCH v4 4/7] target/riscv: Flush TLB only when pmpcfg/pmpaddr really changes

[Weiwei Li <liweiwei@iscas.ac.cn>]

TLB needn't be flushed when pmpcfg/pmpaddr don't changes.

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
---
 target/riscv/pmp.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 9ae3bfea22..0cef9e3e1d 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -26,7 +26,7 @@
 #include "trace.h"
 #include "exec/exec-all.h"
 
-static void pmp_write_cfg(CPURISCVState *env, uint32_t addr_index,
+static bool pmp_write_cfg(CPURISCVState *env, uint32_t addr_index,
                           uint8_t val);
 static uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t addr_index);
 static void pmp_update_rule(CPURISCVState *env, uint32_t pmp_index);
@@ -83,7 +83,7 @@ static inline uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t pmp_index)
  * Accessor to set the cfg reg for a specific PMP/HART
  * Bounds checks and relevant lock bit.
  */
-static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
+static bool pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
 {
     if (pmp_index < MAX_RISCV_PMPS) {
         bool locked = true;
@@ -119,14 +119,17 @@ static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
 
         if (locked) {
             qemu_log_mask(LOG_GUEST_ERROR, "ignoring pmpcfg write - locked\n");
-        } else {
+        } else if (env->pmp_state.pmp[pmp_index].cfg_reg != val) {
             env->pmp_state.pmp[pmp_index].cfg_reg = val;
             pmp_update_rule(env, pmp_index);
+            return true;
         }
     } else {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "ignoring pmpcfg write - out of bounds\n");
     }
+
+    return false;
 }
 
 static void pmp_decode_napot(target_ulong a, target_ulong *sa,
@@ -477,16 +480,19 @@ void pmpcfg_csr_write(CPURISCVState *env, uint32_t reg_index,
     int i;
     uint8_t cfg_val;
     int pmpcfg_nums = 2 << riscv_cpu_mxl(env);
+    bool modified = false;
 
     trace_pmpcfg_csr_write(env->mhartid, reg_index, val);
 
     for (i = 0; i < pmpcfg_nums; i++) {
         cfg_val = (val >> 8 * i)  & 0xff;
-        pmp_write_cfg(env, (reg_index * 4) + i, cfg_val);
+        modified |= pmp_write_cfg(env, (reg_index * 4) + i, cfg_val);
     }
 
     /* If PMP permission of any addr has been changed, flush TLB pages. */
-    tlb_flush(env_cpu(env));
+    if (modified) {
+        tlb_flush(env_cpu(env));
+    }
 }
 
 
@@ -535,9 +541,11 @@ void pmpaddr_csr_write(CPURISCVState *env, uint32_t addr_index,
         }
 
         if (!pmp_is_locked(env, addr_index)) {
-            env->pmp_state.pmp[addr_index].addr_reg = val;
-            pmp_update_rule(env, addr_index);
-            tlb_flush(env_cpu(env));
+            if (env->pmp_state.pmp[addr_index].addr_reg != val) {
+                env->pmp_state.pmp[addr_index].addr_reg = val;
+                pmp_update_rule(env, addr_index);
+                tlb_flush(env_cpu(env));
+            }
         } else {
             qemu_log_mask(LOG_GUEST_ERROR,
                           "ignoring pmpaddr write - locked\n");
-- 
2.25.1