[Qemu-devel] [PATCH v6 22/26] memory: Single byte swap along the I/O path

[<tony.nguyen@bt.com>]

Now that MemOp has been pushed down into the memory API, and
callers are encoding endianness, we can collapse byte swaps
along the I/O path into the accelerator and target independent
adjust_endianness.

Collapsing byte swaps along the I/O path enables additional endian
inversion logic, e.g. SPARC64 Invert Endian TTE bit, with redundant
byte swaps cancelling out.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Tony Nguyen <tony.nguyen@bt.com>
---
 accel/tcg/cputlb.c     | 42 +++------------------------------
 hw/virtio/virtio-pci.c | 10 ++++----
 memory.c               | 33 ++++++++++----------------
 memory_ldst.inc.c      | 64 --------------------------------------------------
 4 files changed, 19 insertions(+), 130 deletions(-)

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 86d85cc..473b8e6 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1200,38 +1200,6 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
     cpu_loop_exit_atomic(env_cpu(env), retaddr);
 }

-#ifdef TARGET_WORDS_BIGENDIAN
-#define NEED_BE_BSWAP 0
-#define NEED_LE_BSWAP 1
-#else
-#define NEED_BE_BSWAP 1
-#define NEED_LE_BSWAP 0
-#endif
-
-/*
- * Byte Swap Helper
- *
- * This should all dead code away depending on the build host and
- * access type.
- */
-
-static inline uint64_t handle_bswap(uint64_t val, MemOp op)
-{
-    if ((memop_big_endian(op) && NEED_BE_BSWAP) ||
-        (!memop_big_endian(op) && NEED_LE_BSWAP)) {
-        switch (op & MO_SIZE) {
-        case MO_8: return val;
-        case MO_16: return bswap16(val);
-        case MO_32: return bswap32(val);
-        case MO_64: return bswap64(val);
-        default:
-            g_assert_not_reached();
-        }
-    } else {
-        return val;
-    }
-}
-
 /*
  * Load Helpers
  *
@@ -1306,10 +1274,8 @@ load_helper(CPUArchState *env, target_ulong addr, TCGMemOpIdx oi,
             }
         }

-        /* FIXME: io_readx ignores MO_BSWAP.  */
-        res = io_readx(env, &env_tlb(env)->d[mmu_idx].iotlb[index],
-                       mmu_idx, addr, retaddr, access_type, op);
-        return handle_bswap(res, op);
+        return io_readx(env, &env_tlb(env)->d[mmu_idx].iotlb[index],
+                        mmu_idx, addr, retaddr, access_type, op);
     }

     /* Handle slow unaligned access (it spans two pages or IO).  */
@@ -1552,10 +1518,8 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
             }
         }

-        /* FIXME: io_writex ignores MO_BSWAP.  */
         io_writex(env, &env_tlb(env)->d[mmu_idx].iotlb[index], mmu_idx,
-                  handle_bswap(val, op),
-                  addr, retaddr, op);
+                  val, addr, retaddr, op);
         return;
     }

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 70eb161..f3fe6ca 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -542,16 +542,15 @@ void virtio_address_space_write(VirtIOPCIProxy *proxy, hwaddr addr,
         val = pci_get_byte(buf);
         break;
     case 2:
-        val = cpu_to_le16(pci_get_word(buf));
+        val = pci_get_word(buf);
         break;
     case 4:
-        val = cpu_to_le32(pci_get_long(buf));
+        val = pci_get_long(buf);
         break;
     default:
         /* As length is under guest control, handle illegal values. */
         return;
     }
-    /* FIXME: memory_region_dispatch_write ignores MO_BSWAP.  */
     memory_region_dispatch_write(mr, addr, val, size_memop(len),
                                  MEMTXATTRS_UNSPECIFIED);
 }
@@ -576,7 +575,6 @@ virtio_address_space_read(VirtIOPCIProxy *proxy, hwaddr addr,
     /* Make sure caller aligned buf properly */
     assert(!(((uintptr_t)buf) & (len - 1)));

-    /* FIXME: memory_region_dispatch_read ignores MO_BSWAP.  */
     memory_region_dispatch_read(mr, addr, &val, size_memop(len),
                                 MEMTXATTRS_UNSPECIFIED);
     switch (len) {
@@ -584,10 +582,10 @@ virtio_address_space_read(VirtIOPCIProxy *proxy, hwaddr addr,
         pci_set_byte(buf, val);
         break;
     case 2:
-        pci_set_word(buf, le16_to_cpu(val));
+        pci_set_word(buf, val);
         break;
     case 4:
-        pci_set_long(buf, le32_to_cpu(val));
+        pci_set_long(buf, val);
         break;
     default:
         /* As length is under guest control, handle illegal values. */
diff --git a/memory.c b/memory.c
index 264c624..9d3c3a6 100644
--- a/memory.c
+++ b/memory.c
@@ -343,32 +343,23 @@ static void flatview_simplify(FlatView *view)
     }
 }

-static bool memory_region_wrong_endianness(MemoryRegion *mr)
+static void adjust_endianness(MemoryRegion *mr, uint64_t *data, MemOp op)
 {
-#ifdef TARGET_WORDS_BIGENDIAN
-    return mr->ops->endianness == MO_LE;
-#else
-    return mr->ops->endianness == MO_BE;
-#endif
-}
-
-static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
-{
-    if (memory_region_wrong_endianness(mr)) {
-        switch (size) {
-        case 1:
+    if ((op & MO_BSWAP) != mr->ops->endianness) {
+        switch (op & MO_SIZE) {
+        case MO_8:
             break;
-        case 2:
+        case MO_16:
             *data = bswap16(*data);
             break;
-        case 4:
+        case MO_32:
             *data = bswap32(*data);
             break;
-        case 8:
+        case MO_64:
             *data = bswap64(*data);
             break;
         default:
-            abort();
+            g_assert_not_reached();
         }
     }
 }
@@ -1446,7 +1437,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
     }

     r = memory_region_dispatch_read1(mr, addr, pval, size, attrs);
-    adjust_endianness(mr, pval, size);
+    adjust_endianness(mr, pval, op);
     return r;
 }

@@ -1489,7 +1480,7 @@ MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
         return MEMTX_DECODE_ERROR;
     }

-    adjust_endianness(mr, &data, size);
+    adjust_endianness(mr, &data, op);

     if ((!kvm_eventfds_enabled()) &&
         memory_region_dispatch_write_eventfds(mr, addr, data, size, attrs)) {
@@ -2335,7 +2326,7 @@ void memory_region_add_eventfd(MemoryRegion *mr,
     }

     if (size) {
-        adjust_endianness(mr, &mrfd.data, size);
+        adjust_endianness(mr, &mrfd.data, size_memop(size));
     }
     memory_region_transaction_begin();
     for (i = 0; i < mr->ioeventfd_nb; ++i) {
@@ -2370,7 +2361,7 @@ void memory_region_del_eventfd(MemoryRegion *mr,
     unsigned i;

     if (size) {
-        adjust_endianness(mr, &mrfd.data, size);
+        adjust_endianness(mr, &mrfd.data, size_memop(size));
     }
     memory_region_transaction_begin();
     for (i = 0; i < mr->ioeventfd_nb; ++i) {
diff --git a/memory_ldst.inc.c b/memory_ldst.inc.c
index ff28b30..33868f7 100644
--- a/memory_ldst.inc.c
+++ b/memory_ldst.inc.c
@@ -37,17 +37,7 @@ static inline uint32_t glue(address_space_ldl_internal, SUFFIX)(ARG1_DECL,
         release_lock |= prepare_mmio_access(mr);

         /* I/O case */
-        /* FIXME: memory_region_dispatch_read ignores MO_BSWAP.  */
         r = memory_region_dispatch_read(mr, addr1, &val, MO_32 | endian, attrs);
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap32(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap32(val);
-        }
-#endif
     } else {
         /* RAM case */
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
@@ -113,17 +103,7 @@ static inline uint64_t glue(address_space_ldq_internal, SUFFIX)(ARG1_DECL,
         release_lock |= prepare_mmio_access(mr);

         /* I/O case */
-        /* FIXME: memory_region_dispatch_read ignores MO_BSWAP.  */
         r = memory_region_dispatch_read(mr, addr1, &val, MO_64 | endian, attrs);
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap64(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap64(val);
-        }
-#endif
     } else {
         /* RAM case */
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
@@ -223,17 +203,7 @@ static inline uint32_t glue(address_space_lduw_internal, SUFFIX)(ARG1_DECL,
         release_lock |= prepare_mmio_access(mr);

         /* I/O case */
-        /* FIXME: memory_region_dispatch_read ignores MO_BSWAP.  */
         r = memory_region_dispatch_read(mr, addr1, &val, MO_16 | endian, attrs);
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap16(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap16(val);
-        }
-#endif
     } else {
         /* RAM case */
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
@@ -299,7 +269,6 @@ void glue(address_space_stl_notdirty, SUFFIX)(ARG1_DECL,
     mr = TRANSLATE(addr, &addr1, &l, true, attrs);
     if (l < 4 || !memory_access_is_direct(mr, true)) {
         release_lock |= prepare_mmio_access(mr);
-
         r = memory_region_dispatch_write(mr, addr1, val, MO_32 | MO_TE, attrs);
     } else {
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
@@ -336,17 +305,6 @@ static inline void glue(address_space_stl_internal, SUFFIX)(ARG1_DECL,
     mr = TRANSLATE(addr, &addr1, &l, true, attrs);
     if (l < 4 || !memory_access_is_direct(mr, true)) {
         release_lock |= prepare_mmio_access(mr);
-
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap32(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap32(val);
-        }
-#endif
-        /* FIXME: memory_region_dispatch_write ignores MO_BSWAP.  */
         r = memory_region_dispatch_write(mr, addr1, val, MO_32 | endian, attrs);
     } else {
         /* RAM case */
@@ -442,17 +400,6 @@ static inline void glue(address_space_stw_internal, SUFFIX)(ARG1_DECL,
     mr = TRANSLATE(addr, &addr1, &l, true, attrs);
     if (l < 2 || !memory_access_is_direct(mr, true)) {
         release_lock |= prepare_mmio_access(mr);
-
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap16(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap16(val);
-        }
-#endif
-        /* FIXME: memory_region_dispatch_write ignores MO_BSWAP.  */
         r = memory_region_dispatch_write(mr, addr1, val, MO_16 | endian, attrs);
     } else {
         /* RAM case */
@@ -516,17 +463,6 @@ static void glue(address_space_stq_internal, SUFFIX)(ARG1_DECL,
     mr = TRANSLATE(addr, &addr1, &l, true, attrs);
     if (l < 8 || !memory_access_is_direct(mr, true)) {
         release_lock |= prepare_mmio_access(mr);
-
-#if defined(TARGET_WORDS_BIGENDIAN)
-        if (endian == MO_LE) {
-            val = bswap64(val);
-        }
-#else
-        if (endian == MO_BE) {
-            val = bswap64(val);
-        }
-#endif
-        /* FIXME: memory_region_dispatch_write ignores MO_BSWAP.  */
         r = memory_region_dispatch_write(mr, addr1, val, MO_64 | endian, attrs);
     } else {
         /* RAM case */
--
1.8.3.1

?