[RFC PATCH 2/4] arm/tcg: add decodetree entry for DSB nXS variant

[Manos Pitsidianakis <manos.pitsidianakis@linaro.org>]

The DSB nXS variant is always both a reads and writes request type.
Ignore the domain field like we do in plain DSB and perform a full
system barrier operation.

The DSB nXS variant is part of FEAT_XS made mandatory from Armv8.7.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 target/arm/tcg/a64.decode      | 3 +++
 target/arm/tcg/translate-a64.c | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/target/arm/tcg/a64.decode b/target/arm/tcg/a64.decode
index 331a8e180c0b14e2abe3ec641a867235574316f7..c4f516abc18224932082cdf3e7530edc7a304bc1 100644
--- a/target/arm/tcg/a64.decode
+++ b/target/arm/tcg/a64.decode
@@ -245,6 +245,9 @@ WFIT            1101 0101 0000 0011 0001 0000 001 rd:5
 
 CLREX           1101 0101 0000 0011 0011 ---- 010 11111
 DSB_DMB         1101 0101 0000 0011 0011 domain:2 types:2 10- 11111
+# For the DSB nXS variant, types always equals MBReqTypes_All and we ignore the
+# domain bits.
+DSB_nXS         1101 0101 0000 0011 0011 -- 10 001 11111
 ISB             1101 0101 0000 0011 0011 ---- 110 11111
 SB              1101 0101 0000 0011 0011 0000 111 11111
 
diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index 071b6349fc38802a62f4b4056e369c4d8b1ecf94..85e71599203eee62b4d22a0b10ed676cc815dab6 100644
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -1959,6 +1959,12 @@ static bool trans_DSB_DMB(DisasContext *s, arg_DSB_DMB *a)
     return true;
 }
 
+static bool trans_DSB_nXS(DisasContext *ctx, arg_DSB_nXS *a)
+{
+    tcg_gen_mb(TCG_BAR_SC | TCG_MO_ALL);
+    return true;
+}
+
 static bool trans_ISB(DisasContext *s, arg_ISB *a)
 {
     /*

-- 
2.45.2