[Qemu-devel] [PATCH v9 18/20] cputlb: Byte swap memory transaction attribute

[Tony Nguyen <tony.nguyen@bt.com>]

Notice new attribute, byte swap, and force the transaction through the
memory slow path.

Required by architectures that can invert endianness of memory
transaction, e.g. SPARC64 has the Invert Endian TTE bit.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Tony Nguyen <tony.nguyen@bt.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/cputlb.c      | 11 +++++++++++
 include/exec/memattrs.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 3c9e634d99..f4573e2c7a 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -738,6 +738,9 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
          */
         address |= TLB_RECHECK;
     }
+    if (attrs.byte_swap) {
+        address |= TLB_FORCE_SLOW;
+    }
     if (!memory_region_is_ram(section->mr) &&
         !memory_region_is_romd(section->mr)) {
         /* IO memory case */
@@ -891,6 +894,10 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
     bool locked = false;
     MemTxResult r;
 
+    if (iotlbentry->attrs.byte_swap) {
+        op ^= MO_BSWAP;
+    }
+
     section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
     mr = section->mr;
     mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
@@ -933,6 +940,10 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
     bool locked = false;
     MemTxResult r;
 
+    if (iotlbentry->attrs.byte_swap) {
+        op ^= MO_BSWAP;
+    }
+
     section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
     mr = section->mr;
     mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
diff --git a/include/exec/memattrs.h b/include/exec/memattrs.h
index d4a3477d71..95f2d20d55 100644
--- a/include/exec/memattrs.h
+++ b/include/exec/memattrs.h
@@ -37,6 +37,8 @@ typedef struct MemTxAttrs {
     unsigned int user:1;
     /* Requester ID (for MSI for example) */
     unsigned int requester_id:16;
+    /* Invert endianness for this page */
+    unsigned int byte_swap:1;
     /*
      * The following are target-specific page-table bits.  These are not
      * related to actual memory transactions at all.  However, this structure
-- 
2.23.0