[PATCH v2 4/6] target/riscv: Implement SMMPT fence instructions

[LIU Zhiwei <zhiwei_liu@linux.alibaba.com>]

This patch completes the SMMPT implementation by adding support for the
new fence instructions: `mfence.spa` and `minval.spa`.

According to the specification, these instructions act as memory ordering
fences for MPT updates. In QEMU's TCG model, this is conservatively
implemented by flushing the entire TLB, which ensures that any subsequent
memory accesses will re-evaluate permissions and see the effects of any prior
MPT modifications.

The instructions are privileged and will cause an illegal instruction
exception if executed outside of M-mode.

Co-authored-by: Huang Tao <eric.huang@linux.alibaba.com>
Co-authored-by: TANG Tiancheng <lyndra@linux.alibaba.com>
Signed-off-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/insn32.decode                    |  2 ++
 .../riscv/insn_trans/trans_privileged.c.inc   | 30 +++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
index cd23b1f3a9..cf58f1beee 100644
--- a/target/riscv/insn32.decode
+++ b/target/riscv/insn32.decode
@@ -120,6 +120,8 @@ sret        0001000    00010 00000 000 00000 1110011
 mret        0011000    00010 00000 000 00000 1110011
 wfi         0001000    00101 00000 000 00000 1110011
 sfence_vma  0001001    ..... ..... 000 00000 1110011 @sfence_vma
+mfence_spa  1000011    ..... ..... 000 00000 1110011 @sfence_vma
+minval_spa  0000011    ..... ..... 000 00000 1110011 @sfence_vma
 
 # *** NMI ***
 mnret       0111000    00010 00000 000 00000 1110011
diff --git a/target/riscv/insn_trans/trans_privileged.c.inc b/target/riscv/insn_trans/trans_privileged.c.inc
index 8a62b4cfcd..5ec6bf5991 100644
--- a/target/riscv/insn_trans/trans_privileged.c.inc
+++ b/target/riscv/insn_trans/trans_privileged.c.inc
@@ -160,3 +160,33 @@ static bool trans_sfence_vma(DisasContext *ctx, arg_sfence_vma *a)
 #endif
     return false;
 }
+
+#define REQUIRE_SMSDID(ctx) do {          \
+    if (!ctx->cfg_ptr->ext_smsdid) {      \
+        return false;                     \
+    }                                     \
+} while (0)
+
+static bool do_mfence_spa(DisasContext *ctx)
+{
+#ifndef CONFIG_USER_ONLY
+    REQUIRE_SMSDID(ctx);
+    if (ctx->priv != PRV_M) {
+        return false;
+    }
+    decode_save_opc(ctx, 0);
+    gen_helper_tlb_flush_all(tcg_env);
+    return true;
+#endif
+    return false;
+}
+
+static bool trans_mfence_spa(DisasContext *ctx, arg_mfence_spa *a)
+{
+    return do_mfence_spa(ctx);
+}
+
+static bool trans_minval_spa(DisasContext *ctx, arg_minval_spa *a)
+{
+    return do_mfence_spa(ctx);
+}
-- 
2.25.1