tcg: Support MMU protection regions smaller than TARGET_PAGE_SIZE

Add support for MMU protection regions that are smaller than
TARGET_PAGE_SIZE. We do this by marking the TLB entry for those
pages with a flag TLB_RECHECK. This flag causes us to always
take the slow-path for accesses. In the slow path we can then
special case them to always call tlb_fill() again, so we have
the correct information for the exact address being accessed.

This change allows us to handle reading and writing from small
regions; we cannot deal with execution from the small region.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180620130619.11362-2-peter.maydell@linaro.org

1 files changed, 16 insertions, 8 deletions

diff --git a/accel/tcg/softmmu_template.h b/accel/tcg/softmmu_template.h
index 239ea6692b..c47591c970 100644
--- a/accel/tcg/softmmu_template.h
+++ b/accel/tcg/softmmu_template.h
@@ -98,10 +98,12 @@
 static inline DATA_TYPE glue(io_read, SUFFIX)(CPUArchState *env,
                                               size_t mmu_idx, size_t index,
                                               target_ulong addr,
-                                              uintptr_t retaddr)
+                                              uintptr_t retaddr,
+                                              bool recheck)
 {
     CPUIOTLBEntry *iotlbentry = &env->iotlb[mmu_idx][index];
-    return io_readx(env, iotlbentry, mmu_idx, addr, retaddr, DATA_SIZE);
+    return io_readx(env, iotlbentry, mmu_idx, addr, retaddr, recheck,
+                    DATA_SIZE);
 }
 #endif
 
@@ -138,7 +140,8 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, target_ulong addr,
 
         /* ??? Note that the io helpers always read data in the target
            byte ordering.  We should push the LE/BE request down into io.  */
-        res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr);
+        res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr,
+                                    tlb_addr & TLB_RECHECK);
         res = TGT_LE(res);
         return res;
     }
@@ -205,7 +208,8 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, target_ulong addr,
 
         /* ??? Note that the io helpers always read data in the target
            byte ordering.  We should push the LE/BE request down into io.  */
-        res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr);
+        res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr,
+                                    tlb_addr & TLB_RECHECK);
         res = TGT_BE(res);
         return res;
     }
@@ -259,10 +263,12 @@ static inline void glue(io_write, SUFFIX)(CPUArchState *env,
                                           size_t mmu_idx, size_t index,
                                           DATA_TYPE val,
                                           target_ulong addr,
-                                          uintptr_t retaddr)
+                                          uintptr_t retaddr,
+                                          bool recheck)
 {
     CPUIOTLBEntry *iotlbentry = &env->iotlb[mmu_idx][index];
-    return io_writex(env, iotlbentry, mmu_idx, val, addr, retaddr, DATA_SIZE);
+    return io_writex(env, iotlbentry, mmu_idx, val, addr, retaddr,
+                     recheck, DATA_SIZE);
 }
 
 void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
@@ -298,7 +304,8 @@ void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
         /* ??? Note that the io helpers always read data in the target
            byte ordering.  We should push the LE/BE request down into io.  */
         val = TGT_LE(val);
-        glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr);
+        glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr,
+                               retaddr, tlb_addr & TLB_RECHECK);
         return;
     }
 
@@ -375,7 +382,8 @@ void helper_be_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
         /* ??? Note that the io helpers always read data in the target
            byte ordering.  We should push the LE/BE request down into io.  */
         val = TGT_BE(val);
-        glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr);
+        glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr,
+                               tlb_addr & TLB_RECHECK);
         return;
     }