target/mips: Simplify and fix update_pagemask

When update_pagemask was split from helper_mtc0_pagemask,
we failed to actually write to the new parameter but continue
to write to env->CP0_PageMask.  Thus the use within
page_table_walk_refill modifies cpu state and not the local
variable as expected.

Simplify by renaming to compute_pagemask and returning the
value directly.  No need for either env or pointer return.

Fixes: 074cfcb4dae ("target/mips: Implement hardware page table walker for MIPS32")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250328175526.368121-4-richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: qemu-stable@nongnu.org

target/mips/tcg/system/cp0_helper.c

@@ -864,24 +864,24 @@ void helper_mtc0_memorymapid(CPUMIPSState *env, target_ulong arg1)
     }
 }
 
-void update_pagemask(CPUMIPSState *env, target_ulong arg1, int32_t *pagemask)
+uint32_t compute_pagemask(uint32_t val)
 {
     /* Don't care MASKX as we don't support 1KB page */
-    uint32_t mask = extract32((uint32_t)arg1, CP0PM_MASK, 16);
+    uint32_t mask = extract32(val, CP0PM_MASK, 16);
     int maskbits = cto32(mask);
 
     /* Ensure no more set bit after first zero, and maskbits even. */
     if ((mask >> maskbits) == 0 && maskbits % 2 == 0) {
-        env->CP0_PageMask = mask << CP0PM_MASK;
+        return mask << CP0PM_MASK;
     } else {
         /* When invalid, set to default target page size. */
-        env->CP0_PageMask = 0;
+        return 0;
     }
 }
 
 void helper_mtc0_pagemask(CPUMIPSState *env, target_ulong arg1)
 {
-    update_pagemask(env, arg1, &env->CP0_PageMask);
+    env->CP0_PageMask = compute_pagemask(arg1);
 }
 
 void helper_mtc0_pagegrain(CPUMIPSState *env, target_ulong arg1)

target/mips/tcg/system/tlb_helper.c

@@ -876,7 +876,7 @@ refill:
         }
     }
     pw_pagemask = m >> TARGET_PAGE_BITS;
-    update_pagemask(env, pw_pagemask << CP0PM_MASK, &pw_pagemask);
+    pw_pagemask = compute_pagemask(pw_pagemask << CP0PM_MASK);
     pw_entryhi = (address & ~0x1fff) | (env->CP0_EntryHi & 0xFF);
     {
         target_ulong tmp_entryhi = env->CP0_EntryHi;

target/mips/tcg/tcg-internal.h

@@ -47,7 +47,7 @@ bool mips_cpu_exec_interrupt(CPUState *cpu, int int_req);
 
 void mmu_init(CPUMIPSState *env, const mips_def_t *def);
 
-void update_pagemask(CPUMIPSState *env, target_ulong arg1, int32_t *pagemask);
+uint32_t compute_pagemask(uint32_t val);
 
 void r4k_invalidate_tlb(CPUMIPSState *env, int idx, int use_extra);
 uint32_t cpu_mips_get_random(CPUMIPSState *env);