Re: [Qemu-devel] [PATCH v5 13/15] cputlb: Byte swap memory transaction attribute

[Richard Henderson]

On 7/25/19 11:48 PM, tony.ngu...@bt.com wrote:
> 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.
> 
> Signed-off-by: Tony Nguyen 
> ---
>  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 e61b1eb..f292a87 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 d4a3477..a0644eb 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;
> +/* SPARC64: TTE invert endianness */
> +unsigned int byte_swap:1;

Don't mention Sparc here, otherwise it seems like it only applies to Sparc,
when it is really a generic feature only currently used by Sparc.

Just say "Invert endianness for this page".

With that,

Reviewed-by: Richard Henderson 


r~

[Qemu-devel] [PATCH v5 13/15] cputlb: Byte swap memory transaction attribute

[tony.nguyen]

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.

Signed-off-by: Tony Nguyen 
---
 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 e61b1eb..f292a87 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 d4a3477..a0644eb 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;
+/* SPARC64: TTE invert endianness */
+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
--
1.8.3.1