target/mips: Require even maskbits in update_pagemask

The number of bits set in PageMask must be even.

Fixes: d40b55bc1b86 ("target/mips: Fix PageMask with variable page size")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250328175526.368121-3-richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: qemu-stable@nongnu.org

1 files changed, 8 insertions, 15 deletions

diff --git a/target/mips/tcg/system/cp0_helper.c b/target/mips/tcg/system/cp0_helper.c
index 8c2114c58a..5db8166d45 100644
--- a/target/mips/tcg/system/cp0_helper.c
+++ b/target/mips/tcg/system/cp0_helper.c
@@ -866,24 +866,17 @@ void helper_mtc0_memorymapid(CPUMIPSState *env, target_ulong arg1)
 
 void update_pagemask(CPUMIPSState *env, target_ulong arg1, int32_t *pagemask)
 {
-    uint32_t mask;
-    int maskbits;
-
     /* Don't care MASKX as we don't support 1KB page */
-    mask = extract32((uint32_t)arg1, CP0PM_MASK, 16);
-    maskbits = cto32(mask);
+    uint32_t mask = extract32((uint32_t)arg1, CP0PM_MASK, 16);
+    int maskbits = cto32(mask);
 
-    /* Ensure no more set bit after first zero */
-    if ((mask >> maskbits) != 0) {
-        goto invalid;
+    /* Ensure no more set bit after first zero, and maskbits even. */
+    if ((mask >> maskbits) == 0 && maskbits % 2 == 0) {
+        env->CP0_PageMask = mask << CP0PM_MASK;
+    } else {
+        /* When invalid, set to default target page size. */
+        env->CP0_PageMask = 0;
     }
-    env->CP0_PageMask = mask << CP0PM_MASK;
-
-    return;
-
-invalid:
-    /* When invalid, set to default target page size. */
-    env->CP0_PageMask = 0;
 }
 
 void helper_mtc0_pagemask(CPUMIPSState *env, target_ulong arg1)