[Qemu-devel] [PULL 2/2] target-mips: flush QEMU TLB when disabling 64-bit addressing

[Leon Alrae]

CP0.Status.KX/SX/UX bits are responsible for enabling access to 64-bit
Kernel/Supervisor/User Segments. If bit is cleared an access to
corresponding segment should generate Address Error Exception.

However, the guest may still be able to access some pages belonging to
the disabled 64-bit segment because we forget to flush QEMU TLB.

This patch fixes it.

Signed-off-by: Leon Alrae <address@hidden>
---
 target-mips/cpu.h       | 18 +++++++++++++++++-
 target-mips/op_helper.c | 13 -------------
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index fa919c1..89c01f7 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -961,6 +961,15 @@ static inline void compute_hflags(CPUMIPSState *env)
 }
 
 #ifndef CONFIG_USER_ONLY
+static inline void cpu_mips_tlb_flush(CPUMIPSState *env, int flush_global)
+{
+    MIPSCPU *cpu = mips_env_get_cpu(env);
+
+    /* Flush qemu's TLB and discard all shadowed entries.  */
+    tlb_flush(CPU(cpu), flush_global);
+    env->tlb->tlb_in_use = env->tlb->nb_tlb;
+}
+
 /* Called for updates to CP0_Status.  */
 static inline void sync_c0_status(CPUMIPSState *env, CPUMIPSState *cpu, int tc)
 {
@@ -999,6 +1008,7 @@ static inline void sync_c0_status(CPUMIPSState *env, 
CPUMIPSState *cpu, int tc)
 static inline void cpu_mips_store_status(CPUMIPSState *env, target_ulong val)
 {
     uint32_t mask = env->CP0_Status_rw_bitmask;
+    target_ulong old = env->CP0_Status;
 
     if (env->insn_flags & ISA_MIPS32R6) {
         bool has_supervisor = extract32(mask, CP0St_KSU, 2) == 0x3;
@@ -1014,7 +1024,13 @@ static inline void cpu_mips_store_status(CPUMIPSState 
*env, target_ulong val)
         mask &= ~(((1 << CP0St_SR) | (1 << CP0St_NMI)) & val);
     }
 
-    env->CP0_Status = (env->CP0_Status & ~mask) | (val & mask);
+    env->CP0_Status = (old & ~mask) | (val & mask);
+#if defined(TARGET_MIPS64)
+    if ((env->CP0_Status ^ old) & (old & (7 << CP0St_UX))) {
+        /* Access to at least one of the 64-bit segments has been disabled */
+        cpu_mips_tlb_flush(env, 1);
+    }
+#endif
     if (env->CP0_Config3 & (1 << CP0C3_MT)) {
         sync_c0_status(env, env, env->current_tc);
     } else {
diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
index 056d53b..d2c98c9 100644
--- a/target-mips/op_helper.c
+++ b/target-mips/op_helper.c
@@ -23,10 +23,6 @@
 #include "exec/cpu_ldst.h"
 #include "sysemu/kvm.h"
 
-#ifndef CONFIG_USER_ONLY
-static inline void cpu_mips_tlb_flush (CPUMIPSState *env, int flush_global);
-#endif
-
 /*****************************************************************************/
 /* Exceptions processing helpers */
 
@@ -1846,15 +1842,6 @@ target_ulong helper_yield(CPUMIPSState *env, 
target_ulong arg)
 
 #ifndef CONFIG_USER_ONLY
 /* TLB management */
-static void cpu_mips_tlb_flush (CPUMIPSState *env, int flush_global)
-{
-    MIPSCPU *cpu = mips_env_get_cpu(env);
-
-    /* Flush qemu's TLB and discard all shadowed entries.  */
-    tlb_flush(CPU(cpu), flush_global);
-    env->tlb->tlb_in_use = env->tlb->nb_tlb;
-}
-
 static void r4k_mips_tlb_flush_extra (CPUMIPSState *env, int first)
 {
     /* Discard entries from env->tlb[first] onwards.  */
-- 
2.1.0