[PATCH v9 0/7] Add RISC-V big-endian target support

[PATCH v9 0/7] Add RISC-V big-endian target support

[Djordje Todorovic]

Rebase on top of master.

Djordje Todorovic (7):
  target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
  target/riscv: Add big-endian CPU configuration field and reset logic
  target/riscv: Implement runtime data endianness via MSTATUS bits
  hw/riscv: Make boot code endianness-aware at runtime
  target/riscv: Fix page table walk endianness for big-endian harts
  target/riscv: Expose big-endian CPU property and add documentation
  target/riscv: Add endianness test for RISC-V BE

 docs/system/target-riscv.rst                  | 24 ++++++
 hw/riscv/boot.c                               | 81 ++++++++++++++++---
 include/hw/riscv/boot.h                       |  1 +
 target/riscv/cpu.c                            | 11 +--
 target/riscv/cpu.h                            | 23 ++++++
 target/riscv/cpu_bits.h                       |  2 +
 target/riscv/cpu_cfg_fields.h.inc             |  1 +
 target/riscv/cpu_helper.c                     | 28 +++++--
 target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
 target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
 target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
 target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
 target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
 target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
 target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
 target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
 target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
 target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
 target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
 target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
 target/riscv/internals.h                      |  9 +--
 target/riscv/tcg/tcg-cpu.c                    |  3 +
 target/riscv/translate.c                      | 22 ++---
 tests/functional/riscv64/meson.build          |  1 +
 tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
 25 files changed, 251 insertions(+), 80 deletions(-)
 create mode 100644 tests/functional/riscv64/test_endianness.py

-- 
2.34.1

[PATCH v9 1/7] target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks

[Djordje Todorovic]

Add the RISC-V privileged ISA defined bit positions for the Supervisor
Big-Endian (SBE, bit 36) and Machine Big-Endian (MBE, bit 37) fields
in the mstatus register. These are used alongside the existing
MSTATUS_UBE (bit 6) to control data endianness at each privilege level.

The MSTATUS_UBE definition was already present, but SBE and MBE were
missing.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/cpu_bits.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index b62dd82fe7..c2a3ee4bf3 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -628,6 +628,8 @@
 #define MSTATUS_TSR         0x00400000 /* since: priv-1.10 */
 #define MSTATUS_SPELP       0x00800000 /* zicfilp */
 #define MSTATUS_SDT         0x01000000
+#define MSTATUS_SBE         0x1000000000ULL
+#define MSTATUS_MBE         0x2000000000ULL
 #define MSTATUS_MPELP       0x020000000000 /* zicfilp */
 #define MSTATUS_GVA         0x4000000000ULL
 #define MSTATUS_MPV         0x8000000000ULL
-- 
2.34.1

[PATCH v9 2/7] target/riscv: Add big-endian CPU configuration field and reset logic

[Djordje Todorovic]

Add a big_endian field to RISCVCPUConfig and wire it into the CPU
reset path. When cfg.big_endian is set, riscv_cpu_reset_hold()
writes 1 into the MSTATUS MBE/SBE/UBE fields using set_field();
otherwise it writes 0. This makes the reset value deterministic on
both cold and warm reset.

The MBE/SBE/UBE bits are not included in the writable mask of any
mstatus/mstatush/sstatus CSR write path (unchanged by this series),
so the value chosen at reset effectively hardwires them per section
3.1.6.5 of the RISC-V Privileged Specification.

The user-facing property and documentation are added in a later
patch, once the full endianness support is in place.

Also update the disassembler comment to clarify that BFD_ENDIAN_LITTLE
is correct because RISC-V instructions are always little-endian per
the ISA specification.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
---
 target/riscv/cpu.c                | 10 +++++-----
 target/riscv/cpu_cfg_fields.h.inc |  1 +
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index ce15a17c37..ae75019186 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -720,6 +720,9 @@ static void riscv_cpu_reset_hold(Object *obj, ResetType type)
             env->mstatus = set_field(env->mstatus, MSTATUS_MDT, 1);
         }
     }
+    env->mstatus = set_field(env->mstatus, MSTATUS_MBE, cpu->cfg.big_endian);
+    env->mstatus = set_field(env->mstatus, MSTATUS_SBE, cpu->cfg.big_endian);
+    env->mstatus = set_field(env->mstatus, MSTATUS_UBE, cpu->cfg.big_endian);
     env->mcause = 0;
     env->miclaim = MIP_SGEIP;
     env->pc = env->resetvec;
@@ -807,11 +810,8 @@ static void riscv_cpu_disas_set_info(const CPUState *s, disassemble_info *info)
     info->target_info = &cpu->cfg;
 
     /*
-     * A couple of bits in MSTATUS set the endianness:
-     *  - MSTATUS_UBE (User-mode),
-     *  - MSTATUS_SBE (Supervisor-mode),
-     *  - MSTATUS_MBE (Machine-mode)
-     * but we don't implement that yet.
+     * RISC-V instructions are always little-endian, regardless of the
+     * data endianness configured via MSTATUS UBE/SBE/MBE bits.
      */
     info->endian = BFD_ENDIAN_LITTLE;
 
diff --git a/target/riscv/cpu_cfg_fields.h.inc b/target/riscv/cpu_cfg_fields.h.inc
index 734fa079f2..9eb47af0a7 100644
--- a/target/riscv/cpu_cfg_fields.h.inc
+++ b/target/riscv/cpu_cfg_fields.h.inc
@@ -157,6 +157,7 @@ BOOL_FIELD(ext_xmipscmov)
 BOOL_FIELD(ext_xmipslsp)
 BOOL_FIELD(ext_xlrbr)
 
+BOOL_FIELD(big_endian)
 BOOL_FIELD(mmu)
 BOOL_FIELD(pmp)
 BOOL_FIELD(debug)
-- 
2.34.1

[PATCH v9 3/7] target/riscv: Implement runtime data endianness via MSTATUS bits

[Djordje Todorovic]

Make data accesses honour the MSTATUS MBE/SBE/UBE endianness bits
instead of being hardcoded to little-endian. A new helper,
riscv_cpu_data_is_big_endian(), picks the bit corresponding to the
current privilege level (MBE for M, SBE for S, UBE for U). The
existing mo_endian_env() wrapper in internals.h now returns MO_BE or
MO_LE based on that helper, so the hypervisor load/store helpers in
op_helper.c pick up the runtime endianness automatically.

On the translator side, DisasContext gains a mo_endianness field
holding MO_BE or MO_LE, which the generated load/store ops OR into
their MemOp. The trivial mo_endian() wrapper is dropped and call
sites reference ctx->mo_endianness directly.

TB_FLAGS has no free bits, so the endianness is carried into the
translator through bit 32 of cs_base (alongside misa_ext in bits
0-25). This keys TBs correctly on the current data endianness. The
cs_base comment in include/exec/translation-block.h is updated to
document the RISC-V usage.

Instruction fetches remain MO_LE unconditionally; RISC-V instructions
are always little-endian per the ISA specification.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
---
 target/riscv/cpu.h                            | 23 +++++++++++++++++++
 target/riscv/insn_trans/trans_rva.c.inc       |  4 ++--
 target/riscv/insn_trans/trans_rvd.c.inc       |  4 ++--
 target/riscv/insn_trans/trans_rvf.c.inc       |  4 ++--
 target/riscv/insn_trans/trans_rvi.c.inc       |  8 +++----
 target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 ++--
 target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 ++--
 target/riscv/insn_trans/trans_rvzce.c.inc     |  4 ++--
 target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 ++--
 target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 ++--
 target/riscv/insn_trans/trans_xmips.c.inc     |  8 +++----
 target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++++++-------
 target/riscv/insn_trans/trans_zilsd.c.inc     |  4 ++--
 target/riscv/internals.h                      |  9 +-------
 target/riscv/tcg/tcg-cpu.c                    |  3 +++
 target/riscv/translate.c                      | 22 ++++++------------
 16 files changed, 68 insertions(+), 57 deletions(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 81c41e3429..1f2d0777e8 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -705,6 +705,7 @@ FIELD(TB_FLAGS, PM_SIGNEXTEND, 31, 1)
 
 FIELD(EXT_TB_FLAGS, MISA_EXT, 0, 32)
 FIELD(EXT_TB_FLAGS, ALTFMT, 32, 1)
+FIELD(EXT_TB_FLAGS, BIG_ENDIAN, 33, 1)
 
 #ifdef TARGET_RISCV32
 #define riscv_cpu_mxl(env)  ((void)(env), MXL_RV32)
@@ -721,6 +722,28 @@ static inline const RISCVCPUConfig *riscv_cpu_cfg(CPURISCVState *env)
     return &env_archcpu(env)->cfg;
 }
 
+/*
+ * Return true if data accesses are big-endian for the current privilege
+ * level, based on the MSTATUS MBE/SBE/UBE bits.
+ */
+static inline bool riscv_cpu_data_is_big_endian(CPURISCVState *env)
+{
+#if defined(CONFIG_USER_ONLY)
+    return false;
+#else
+    switch (env->priv) {
+    case PRV_M:
+        return env->mstatus & MSTATUS_MBE;
+    case PRV_S:
+        return env->mstatus & MSTATUS_SBE;
+    case PRV_U:
+        return env->mstatus & MSTATUS_UBE;
+    default:
+        g_assert_not_reached();
+    }
+#endif
+}
+
 #if !defined(CONFIG_USER_ONLY)
 static inline int cpu_address_mode(CPURISCVState *env)
 {
diff --git a/target/riscv/insn_trans/trans_rva.c.inc b/target/riscv/insn_trans/trans_rva.c.inc
index 62c0fe673d..44c1696fe4 100644
--- a/target/riscv/insn_trans/trans_rva.c.inc
+++ b/target/riscv/insn_trans/trans_rva.c.inc
@@ -35,7 +35,7 @@ static bool gen_lr(DisasContext *ctx, arg_atomic *a, MemOp mop)
     TCGv src1;
 
     mop |= MO_ALIGN;
-    mop |= mo_endian(ctx);
+    mop |= ctx->mo_endianness;
 
     decode_save_opc(ctx, 0);
     src1 = get_address(ctx, a->rs1, 0);
@@ -65,7 +65,7 @@ static bool gen_sc(DisasContext *ctx, arg_atomic *a, MemOp mop)
     TCGLabel *l2 = gen_new_label();
 
     mop |= MO_ALIGN;
-    mop |= mo_endian(ctx);
+    mop |= ctx->mo_endianness;
 
     decode_save_opc(ctx, 0);
     src1 = get_address(ctx, a->rs1, 0);
diff --git a/target/riscv/insn_trans/trans_rvd.c.inc b/target/riscv/insn_trans/trans_rvd.c.inc
index ffea0c2a1f..3b9a745520 100644
--- a/target/riscv/insn_trans/trans_rvd.c.inc
+++ b/target/riscv/insn_trans/trans_rvd.c.inc
@@ -60,7 +60,7 @@ static bool trans_fld(DisasContext *ctx, arg_fld *a)
     } else {
         memop |= MO_ATOM_IFALIGN;
     }
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
 
     decode_save_opc(ctx, 0);
     addr = get_address(ctx, a->rs1, a->imm);
@@ -85,7 +85,7 @@ static bool trans_fsd(DisasContext *ctx, arg_fsd *a)
     } else {
         memop |= MO_ATOM_IFALIGN;
     }
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
 
     decode_save_opc(ctx, 0);
     addr = get_address(ctx, a->rs1, a->imm);
diff --git a/target/riscv/insn_trans/trans_rvf.c.inc b/target/riscv/insn_trans/trans_rvf.c.inc
index 89fb0f604a..e935523c93 100644
--- a/target/riscv/insn_trans/trans_rvf.c.inc
+++ b/target/riscv/insn_trans/trans_rvf.c.inc
@@ -48,7 +48,7 @@ static bool trans_flw(DisasContext *ctx, arg_flw *a)
     REQUIRE_FPU;
     REQUIRE_EXT(ctx, RVF);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     if (ctx->cfg_ptr->ext_zama16b) {
         memop |= MO_ATOM_WITHIN16;
     }
@@ -71,7 +71,7 @@ static bool trans_fsw(DisasContext *ctx, arg_fsw *a)
     REQUIRE_FPU;
     REQUIRE_EXT(ctx, RVF);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     if (ctx->cfg_ptr->ext_zama16b) {
         memop |= MO_ATOM_WITHIN16;
     }
diff --git a/target/riscv/insn_trans/trans_rvi.c.inc b/target/riscv/insn_trans/trans_rvi.c.inc
index 2c82ae41a7..2de74fac3a 100644
--- a/target/riscv/insn_trans/trans_rvi.c.inc
+++ b/target/riscv/insn_trans/trans_rvi.c.inc
@@ -392,7 +392,7 @@ static bool gen_load_i128(DisasContext *ctx, arg_lb *a, MemOp memop)
         }
     } else {
         tcg_gen_qemu_ld_i128(t16, addrl, ctx->mem_idx, memop);
-        if (mo_endian(ctx) == MO_LE) {
+        if (ctx->mo_endianness == MO_LE) {
             tcg_gen_extr_i128_i64(tl, th, t16);
         } else {
             tcg_gen_extr_i128_i64(th, tl, t16);
@@ -409,7 +409,7 @@ static bool gen_load(DisasContext *ctx, arg_lb *a, MemOp memop)
 {
     bool out;
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     if (ctx->cfg_ptr->ext_zama16b) {
         memop |= MO_ATOM_WITHIN16;
     }
@@ -508,7 +508,7 @@ static bool gen_store_i128(DisasContext *ctx, arg_sb *a, MemOp memop)
         tcg_gen_ext_tl_i64(tl, src2l);
         tcg_gen_ext_tl_i64(th, src2h);
 
-        if (mo_endian(ctx) == MO_LE) {
+        if (ctx->mo_endianness == MO_LE) {
             tcg_gen_concat_i64_i128(t16, tl, th);
         } else {
             tcg_gen_concat_i64_i128(t16, th, tl);
@@ -520,7 +520,7 @@ static bool gen_store_i128(DisasContext *ctx, arg_sb *a, MemOp memop)
 
 static bool gen_store(DisasContext *ctx, arg_sb *a, MemOp memop)
 {
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     if (ctx->cfg_ptr->ext_zama16b) {
         memop |= MO_ATOM_WITHIN16;
     }
diff --git a/target/riscv/insn_trans/trans_rvzacas.c.inc b/target/riscv/insn_trans/trans_rvzacas.c.inc
index 8d94b83ce9..79bca1e957 100644
--- a/target/riscv/insn_trans/trans_rvzacas.c.inc
+++ b/target/riscv/insn_trans/trans_rvzacas.c.inc
@@ -76,7 +76,7 @@ static bool gen_cmpxchg64(DisasContext *ctx, arg_atomic *a, MemOp mop)
     TCGv src1 = get_address(ctx, a->rs1, 0);
     TCGv_i64 src2 = get_gpr_pair(ctx, a->rs2);
 
-    mop |= mo_endian(ctx);
+    mop |= ctx->mo_endianness;
     decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
     tcg_gen_atomic_cmpxchg_i64(dest, src1, dest, src2, ctx->mem_idx, mop);
 
@@ -121,7 +121,7 @@ static bool trans_amocas_q(DisasContext *ctx, arg_amocas_q *a)
     TCGv_i64 desth = get_gpr(ctx, a->rd == 0 ? 0 : a->rd + 1, EXT_NONE);
     MemOp memop = MO_ALIGN | MO_UO;
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_concat_i64_i128(src2, src2l, src2h);
     tcg_gen_concat_i64_i128(dest, destl, desth);
     decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
diff --git a/target/riscv/insn_trans/trans_rvzalasr.c.inc b/target/riscv/insn_trans/trans_rvzalasr.c.inc
index 0f307affec..79b0b2c63b 100644
--- a/target/riscv/insn_trans/trans_rvzalasr.c.inc
+++ b/target/riscv/insn_trans/trans_rvzalasr.c.inc
@@ -29,7 +29,7 @@ static bool gen_load_acquire(DisasContext *ctx, arg_lb_aqrl *a, MemOp memop)
         return false;
     }
 
-    memop |= MO_ALIGN | mo_endian(ctx);
+    memop |= MO_ALIGN | ctx->mo_endianness;
     memop |= (ctx->cfg_ptr->ext_zama16b) ? MO_ATOM_WITHIN16 : 0;
 
     tcg_gen_qemu_ld_tl(dest, addr, ctx->mem_idx, memop);
@@ -79,7 +79,7 @@ static bool gen_store_release(DisasContext *ctx, arg_sb_aqrl *a, MemOp memop)
         return false;
     }
 
-    memop |= MO_ALIGN | mo_endian(ctx);
+    memop |= MO_ALIGN | ctx->mo_endianness;
     memop |= (ctx->cfg_ptr->ext_zama16b) ? MO_ATOM_WITHIN16 : 0;
 
     /* Add a memory barrier implied by RL (mandatory) and AQ (optional) */
diff --git a/target/riscv/insn_trans/trans_rvzce.c.inc b/target/riscv/insn_trans/trans_rvzce.c.inc
index 0d3ba40e52..71b4ca5473 100644
--- a/target/riscv/insn_trans/trans_rvzce.c.inc
+++ b/target/riscv/insn_trans/trans_rvzce.c.inc
@@ -185,7 +185,7 @@ static bool gen_pop(DisasContext *ctx, arg_cmpp *a, bool ret, bool ret_val)
 
     tcg_gen_addi_tl(addr, sp, stack_adj - reg_size);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     for (i = X_Sn + 11; i >= 0; i--) {
         if (reg_bitmap & (1 << i)) {
             TCGv dest = dest_gpr(ctx, i);
@@ -239,7 +239,7 @@ static bool trans_cm_push(DisasContext *ctx, arg_cm_push *a)
 
     tcg_gen_subi_tl(addr, sp, reg_size);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     for (i = X_Sn + 11; i >= 0; i--) {
         if (reg_bitmap & (1 << i)) {
             TCGv val = get_gpr(ctx, i, EXT_NONE);
diff --git a/target/riscv/insn_trans/trans_rvzfh.c.inc b/target/riscv/insn_trans/trans_rvzfh.c.inc
index 791ee51f65..f36b46c211 100644
--- a/target/riscv/insn_trans/trans_rvzfh.c.inc
+++ b/target/riscv/insn_trans/trans_rvzfh.c.inc
@@ -49,7 +49,7 @@ static bool trans_flh(DisasContext *ctx, arg_flh *a)
     REQUIRE_FPU;
     REQUIRE_ZFHMIN_OR_ZFBFMIN(ctx);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     decode_save_opc(ctx, 0);
     t0 = get_gpr(ctx, a->rs1, EXT_NONE);
     if (a->imm) {
@@ -74,7 +74,7 @@ static bool trans_fsh(DisasContext *ctx, arg_fsh *a)
     REQUIRE_FPU;
     REQUIRE_ZFHMIN_OR_ZFBFMIN(ctx);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     decode_save_opc(ctx, 0);
     t0 = get_gpr(ctx, a->rs1, EXT_NONE);
     if (a->imm) {
diff --git a/target/riscv/insn_trans/trans_rvzicfiss.c.inc b/target/riscv/insn_trans/trans_rvzicfiss.c.inc
index 0b6ad57965..43f586dce9 100644
--- a/target/riscv/insn_trans/trans_rvzicfiss.c.inc
+++ b/target/riscv/insn_trans/trans_rvzicfiss.c.inc
@@ -105,7 +105,7 @@ static bool trans_ssamoswap_w(DisasContext *ctx, arg_amoswap_w *a)
     decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
     src1 = get_address(ctx, a->rs1, 0);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_atomic_xchg_tl(dest, src1, src2, SS_MMU_INDEX(ctx), memop);
     gen_set_gpr(ctx, a->rd, dest);
     return true;
@@ -135,7 +135,7 @@ static bool trans_ssamoswap_d(DisasContext *ctx, arg_amoswap_w *a)
     decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
     src1 = get_address(ctx, a->rs1, 0);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_atomic_xchg_tl(dest, src1, src2, SS_MMU_INDEX(ctx), memop);
     gen_set_gpr(ctx, a->rd, dest);
     return true;
diff --git a/target/riscv/insn_trans/trans_xmips.c.inc b/target/riscv/insn_trans/trans_xmips.c.inc
index c1a30156d3..1b9993a9b0 100644
--- a/target/riscv/insn_trans/trans_xmips.c.inc
+++ b/target/riscv/insn_trans/trans_xmips.c.inc
@@ -47,7 +47,7 @@ static bool trans_ccmov(DisasContext *ctx, arg_ccmov *a)
 /* Load Doubleword Pair. */
 static bool trans_ldp(DisasContext *ctx, arg_ldp *a)
 {
-    MemOp memop = MO_SQ | mo_endian(ctx);
+    MemOp memop = MO_SQ | ctx->mo_endianness;
 
     REQUIRE_XMIPSLSP(ctx);
     REQUIRE_64_OR_128BIT(ctx);
@@ -71,7 +71,7 @@ static bool trans_ldp(DisasContext *ctx, arg_ldp *a)
 /* Load Word Pair. */
 static bool trans_lwp(DisasContext *ctx, arg_lwp *a)
 {
-    MemOp memop = MO_SL | mo_endian(ctx);
+    MemOp memop = MO_SL | ctx->mo_endianness;
 
     REQUIRE_XMIPSLSP(ctx);
 
@@ -94,7 +94,7 @@ static bool trans_lwp(DisasContext *ctx, arg_lwp *a)
 /* Store Doubleword Pair. */
 static bool trans_sdp(DisasContext *ctx, arg_sdp *a)
 {
-    MemOp memop = MO_UQ | mo_endian(ctx);
+    MemOp memop = MO_UQ | ctx->mo_endianness;
 
     REQUIRE_XMIPSLSP(ctx);
     REQUIRE_64_OR_128BIT(ctx);
@@ -116,7 +116,7 @@ static bool trans_sdp(DisasContext *ctx, arg_sdp *a)
 /* Store Word Pair. */
 static bool trans_swp(DisasContext *ctx, arg_swp *a)
 {
-    MemOp memop = MO_SL | mo_endian(ctx);
+    MemOp memop = MO_SL | ctx->mo_endianness;
 
     REQUIRE_XMIPSLSP(ctx);
 
diff --git a/target/riscv/insn_trans/trans_xthead.c.inc b/target/riscv/insn_trans/trans_xthead.c.inc
index f8b95c6498..f4e3051000 100644
--- a/target/riscv/insn_trans/trans_xthead.c.inc
+++ b/target/riscv/insn_trans/trans_xthead.c.inc
@@ -349,7 +349,7 @@ static bool gen_fload_idx(DisasContext *ctx, arg_th_memidx *a, MemOp memop,
     TCGv_i64 rd = cpu_fpr[a->rd];
     TCGv addr = get_th_address_indexed(ctx, a->rs1, a->rs2, a->imm2, zext_offs);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_ld_i64(rd, addr, ctx->mem_idx, memop);
     if ((memop & MO_SIZE) == MO_32) {
         gen_nanbox_s(rd, rd);
@@ -370,7 +370,7 @@ static bool gen_fstore_idx(DisasContext *ctx, arg_th_memidx *a, MemOp memop,
     TCGv_i64 rd = cpu_fpr[a->rd];
     TCGv addr = get_th_address_indexed(ctx, a->rs1, a->rs2, a->imm2, zext_offs);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_st_i64(rd, addr, ctx->mem_idx, memop);
 
     return true;
@@ -570,7 +570,7 @@ static bool gen_load_inc(DisasContext *ctx, arg_th_meminc *a, MemOp memop,
     TCGv rd = dest_gpr(ctx, a->rd);
     TCGv rs1 = get_gpr(ctx, a->rs1, EXT_NONE);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_ld_tl(rd, addr, ctx->mem_idx, memop);
     tcg_gen_addi_tl(rs1, rs1, imm);
     gen_set_gpr(ctx, a->rd, rd);
@@ -591,7 +591,7 @@ static bool gen_store_inc(DisasContext *ctx, arg_th_meminc *a, MemOp memop,
     TCGv data = get_gpr(ctx, a->rd, EXT_NONE);
     TCGv rs1 = get_gpr(ctx, a->rs1, EXT_NONE);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_st_tl(data, addr, ctx->mem_idx, memop);
     tcg_gen_addi_tl(rs1, rs1, imm);
     gen_set_gpr(ctx, a->rs1, rs1);
@@ -747,7 +747,7 @@ static bool gen_load_idx(DisasContext *ctx, arg_th_memidx *a, MemOp memop,
     TCGv rd = dest_gpr(ctx, a->rd);
     TCGv addr = get_th_address_indexed(ctx, a->rs1, a->rs2, a->imm2, zext_offs);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_ld_tl(rd, addr, ctx->mem_idx, memop);
     gen_set_gpr(ctx, a->rd, rd);
 
@@ -765,7 +765,7 @@ static bool gen_store_idx(DisasContext *ctx, arg_th_memidx *a, MemOp memop,
     TCGv data = get_gpr(ctx, a->rd, EXT_NONE);
     TCGv addr = get_th_address_indexed(ctx, a->rs1, a->rs2, a->imm2, zext_offs);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_st_tl(data, addr, ctx->mem_idx, memop);
 
     return true;
@@ -926,7 +926,7 @@ static bool gen_loadpair_tl(DisasContext *ctx, arg_th_pair *a, MemOp memop,
     addr1 = get_address(ctx, a->rs, imm);
     addr2 = get_address(ctx, a->rs, memop_size(memop) + imm);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_ld_tl(t1, addr1, ctx->mem_idx, memop);
     tcg_gen_qemu_ld_tl(t2, addr2, ctx->mem_idx, memop);
     gen_set_gpr(ctx, a->rd1, t1);
@@ -965,7 +965,7 @@ static bool gen_storepair_tl(DisasContext *ctx, arg_th_pair *a, MemOp memop,
     addr1 = get_address(ctx, a->rs, imm);
     addr2 = get_address(ctx, a->rs, memop_size(memop) + imm);
 
-    memop |= mo_endian(ctx);
+    memop |= ctx->mo_endianness;
     tcg_gen_qemu_st_tl(data1, addr1, ctx->mem_idx, memop);
     tcg_gen_qemu_st_tl(data2, addr2, ctx->mem_idx, memop);
     return true;
diff --git a/target/riscv/insn_trans/trans_zilsd.c.inc b/target/riscv/insn_trans/trans_zilsd.c.inc
index f50c52f22c..8068cc1aec 100644
--- a/target/riscv/insn_trans/trans_zilsd.c.inc
+++ b/target/riscv/insn_trans/trans_zilsd.c.inc
@@ -30,7 +30,7 @@ static bool gen_load_i64(DisasContext *ctx, arg_ld *a)
     TCGv addr = get_address(ctx, a->rs1, a->imm);
     TCGv_i64 tmp = tcg_temp_new_i64();
 
-    tcg_gen_qemu_ld_i64(tmp, addr, ctx->mem_idx, MO_SQ | mo_endian(ctx));
+    tcg_gen_qemu_ld_i64(tmp, addr, ctx->mem_idx, MO_SQ | ctx->mo_endianness);
 
     if (a->rd == 0) {
         return true;
@@ -85,7 +85,7 @@ static bool gen_store_i64(DisasContext *ctx, arg_sd *a)
     } else {
         tcg_gen_concat_tl_i64(tmp, data_low, data_high);
     }
-    tcg_gen_qemu_st_i64(tmp, addr, ctx->mem_idx, MO_SQ | mo_endian(ctx));
+    tcg_gen_qemu_st_i64(tmp, addr, ctx->mem_idx, MO_SQ | ctx->mo_endianness);
 
     return true;
 }
diff --git a/target/riscv/internals.h b/target/riscv/internals.h
index bac6c8032a..dc505a9ab3 100644
--- a/target/riscv/internals.h
+++ b/target/riscv/internals.h
@@ -64,14 +64,7 @@ static inline bool mmuidx_2stage(int mmu_idx)
 
 static inline MemOp mo_endian_env(CPURISCVState *env)
 {
-    /*
-     * A couple of bits in MSTATUS set the endianness:
-     *  - MSTATUS_UBE (User-mode),
-     *  - MSTATUS_SBE (Supervisor-mode),
-     *  - MSTATUS_MBE (Machine-mode)
-     * but we don't implement that yet.
-     */
-    return MO_LE;
+    return riscv_cpu_data_is_big_endian(env) ? MO_BE : MO_LE;
 }
 
 /* share data between vector helpers and decode code */
diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 02c98cc2db..81b56e5a62 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -193,6 +193,9 @@ static TCGTBCPUState riscv_get_tb_cpu_state(CPUState *cs)
     flags = FIELD_DP32(flags, TB_FLAGS, PM_SIGNEXTEND, pm_signext);
 
     ext_flags = FIELD_DP64(ext_flags, EXT_TB_FLAGS, MISA_EXT, env->misa_ext);
+    if (riscv_cpu_data_is_big_endian(env)) {
+        ext_flags = FIELD_DP64(ext_flags, EXT_TB_FLAGS, BIG_ENDIAN, 1);
+    }
 
     return (TCGTBCPUState){
         .pc = env->xl == MXL_RV32 ? env->pc & UINT32_MAX : env->pc,
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 1e4f340256..35c6b37c0b 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -120,6 +120,8 @@ typedef struct DisasContext {
     bool fcfi_lp_expected;
     /* zicfiss extension, if shadow stack was enabled during TB gen */
     bool bcfi_enabled;
+    /* Data endianness from MSTATUS UBE/SBE/MBE */
+    MemOp mo_endianness;
 } DisasContext;
 
 static inline bool has_ext(DisasContext *ctx, uint32_t ext)
@@ -127,18 +129,6 @@ static inline bool has_ext(DisasContext *ctx, uint32_t ext)
     return ctx->misa_ext & ext;
 }
 
-static inline MemOp mo_endian(DisasContext *ctx)
-{
-    /*
-     * A couple of bits in MSTATUS set the endianness:
-     *  - MSTATUS_UBE (User-mode),
-     *  - MSTATUS_SBE (Supervisor-mode),
-     *  - MSTATUS_MBE (Machine-mode)
-     * but we don't implement that yet.
-     */
-    return MO_LE;
-}
-
 #ifdef TARGET_RISCV32
 #define get_xl(ctx)    MXL_RV32
 #elif defined(CONFIG_USER_ONLY)
@@ -155,7 +145,7 @@ static inline MemOp mo_endian(DisasContext *ctx)
 #define get_address_xl(ctx)    ((ctx)->address_xl)
 #endif
 
-#define mxl_memop(ctx) ((get_xl(ctx) + 1) | mo_endian(ctx))
+#define mxl_memop(ctx) ((get_xl(ctx) + 1) | (ctx)->mo_endianness)
 
 /* The word size for this machine mode. */
 static inline int __attribute__((unused)) get_xlen(DisasContext *ctx)
@@ -1156,7 +1146,7 @@ static bool gen_amo(DisasContext *ctx, arg_atomic *a,
     TCGv src1, src2 = get_gpr(ctx, a->rs2, EXT_NONE);
     MemOp size = mop & MO_SIZE;
 
-    mop |= mo_endian(ctx);
+    mop |= ctx->mo_endianness;
     if (ctx->cfg_ptr->ext_zama16b && size >= MO_32) {
         mop |= MO_ATOM_WITHIN16;
     } else {
@@ -1177,7 +1167,7 @@ static bool gen_cmpxchg(DisasContext *ctx, arg_atomic *a, MemOp mop)
     TCGv src1 = get_address(ctx, a->rs1, 0);
     TCGv src2 = get_gpr(ctx, a->rs2, EXT_NONE);
 
-    mop |= mo_endian(ctx);
+    mop |= ctx->mo_endianness;
     decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
     tcg_gen_atomic_cmpxchg_tl(dest, src1, dest, src2, ctx->mem_idx, mop);
 
@@ -1360,6 +1350,8 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     ctx->zero = tcg_constant_tl(0);
     ctx->virt_inst_excp = false;
     ctx->decoders = cpu->decoders;
+    ctx->mo_endianness = FIELD_EX64(ext_tb_flags, EXT_TB_FLAGS, BIG_ENDIAN)
+                         ? MO_BE : MO_LE;
 }
 
 static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)
-- 
2.34.1

[PATCH v9 4/7] hw/riscv: Make boot code endianness-aware at runtime

[Djordje Todorovic]

Add riscv_is_big_endian() helper that checks the hart's big-endian CPU
property and use it throughout the boot code:

- ELF loading: pass ELFDATA2MSB or ELFDATA2LSB based on endianness
- Firmware dynamic info: use cpu_to_be* or cpu_to_le* based on endianness
- Reset vector: instructions (entries 0-5) remain always little-endian,
  data words (entries 6-9) use target data endianness. For RV64 BE, the
  hi/lo word pairs within each dword are swapped since LD reads as BE.

This is part of the runtime big-endian support series which avoids
separate BE binaries by handling endianness as a CPU property.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
---
 hw/riscv/boot.c         | 81 +++++++++++++++++++++++++++++++++++------
 include/hw/riscv/boot.h |  1 +
 2 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
index 9086793b7a..37b8f3dfa7 100644
--- a/hw/riscv/boot.c
+++ b/hw/riscv/boot.c
@@ -40,6 +40,28 @@ bool riscv_is_32bit(RISCVHartArrayState *harts)
     return mcc->def->misa_mxl_max == MXL_RV32;
 }
 
+bool riscv_is_big_endian(RISCVHartArrayState *harts)
+{
+    return harts->harts[0].cfg.big_endian;
+}
+
+/*
+ * Convert a pair of 32-bit words forming a 64-bit dword to target data
+ * endianness. For big-endian, the hi/lo word order is swapped since LD
+ * interprets bytes as BE.
+ */
+static void riscv_boot_data_dword(uint32_t *data, bool big_endian)
+{
+    if (big_endian) {
+        uint32_t tmp = data[0];
+        data[0] = cpu_to_be32(data[1]);
+        data[1] = cpu_to_be32(tmp);
+    } else {
+        data[0] = cpu_to_le32(data[0]);
+        data[1] = cpu_to_le32(data[1]);
+    }
+}
+
 /*
  * Return the per-socket PLIC hart topology configuration string
  * (caller must free with g_free())
@@ -262,8 +284,9 @@ void riscv_load_kernel(MachineState *machine,
      */
     kernel_size = load_elf_ram_sym(kernel_filename, NULL, NULL, NULL, NULL,
                                    &info->image_low_addr, &info->image_high_addr,
-                                   NULL, ELFDATA2LSB, EM_RISCV,
-                                   1, 0, NULL, true, sym_cb);
+                                   NULL,
+                                   ELFDATA2LSB,
+                                   EM_RISCV, 1, 0, NULL, true, sym_cb);
     if (kernel_size > 0) {
         info->kernel_size = kernel_size;
         goto out;
@@ -406,21 +429,32 @@ void riscv_rom_copy_firmware_info(MachineState *machine,
     struct fw_dynamic_info64 dinfo64;
     void *dinfo_ptr = NULL;
     size_t dinfo_len;
+    bool big_endian = riscv_is_big_endian(harts);
 
     if (riscv_is_32bit(harts)) {
-        dinfo32.magic = cpu_to_le32(FW_DYNAMIC_INFO_MAGIC_VALUE);
-        dinfo32.version = cpu_to_le32(FW_DYNAMIC_INFO_VERSION);
-        dinfo32.next_mode = cpu_to_le32(FW_DYNAMIC_INFO_NEXT_MODE_S);
-        dinfo32.next_addr = cpu_to_le32(kernel_entry);
+        dinfo32.magic = big_endian ? cpu_to_be32(FW_DYNAMIC_INFO_MAGIC_VALUE)
+                                   : cpu_to_le32(FW_DYNAMIC_INFO_MAGIC_VALUE);
+        dinfo32.version = big_endian ? cpu_to_be32(FW_DYNAMIC_INFO_VERSION)
+                                     : cpu_to_le32(FW_DYNAMIC_INFO_VERSION);
+        dinfo32.next_mode = big_endian
+                          ? cpu_to_be32(FW_DYNAMIC_INFO_NEXT_MODE_S)
+                          : cpu_to_le32(FW_DYNAMIC_INFO_NEXT_MODE_S);
+        dinfo32.next_addr = big_endian ? cpu_to_be32(kernel_entry)
+                                       : cpu_to_le32(kernel_entry);
         dinfo32.options = 0;
         dinfo32.boot_hart = 0;
         dinfo_ptr = &dinfo32;
         dinfo_len = sizeof(dinfo32);
     } else {
-        dinfo64.magic = cpu_to_le64(FW_DYNAMIC_INFO_MAGIC_VALUE);
-        dinfo64.version = cpu_to_le64(FW_DYNAMIC_INFO_VERSION);
-        dinfo64.next_mode = cpu_to_le64(FW_DYNAMIC_INFO_NEXT_MODE_S);
-        dinfo64.next_addr = cpu_to_le64(kernel_entry);
+        dinfo64.magic = big_endian ? cpu_to_be64(FW_DYNAMIC_INFO_MAGIC_VALUE)
+                                   : cpu_to_le64(FW_DYNAMIC_INFO_MAGIC_VALUE);
+        dinfo64.version = big_endian ? cpu_to_be64(FW_DYNAMIC_INFO_VERSION)
+                                     : cpu_to_le64(FW_DYNAMIC_INFO_VERSION);
+        dinfo64.next_mode = big_endian
+                          ? cpu_to_be64(FW_DYNAMIC_INFO_NEXT_MODE_S)
+                          : cpu_to_le64(FW_DYNAMIC_INFO_NEXT_MODE_S);
+        dinfo64.next_addr = big_endian ? cpu_to_be64(kernel_entry)
+                                       : cpu_to_le64(kernel_entry);
         dinfo64.options = 0;
         dinfo64.boot_hart = 0;
         dinfo_ptr = &dinfo64;
@@ -489,10 +523,33 @@ void riscv_setup_rom_reset_vec(MachineState *machine, RISCVHartArrayState *harts
         reset_vec[2] = 0x00000013;   /*     addi   x0, x0, 0 */
     }
 
-    /* copy in the reset vector in little_endian byte order */
-    for (i = 0; i < ARRAY_SIZE(reset_vec); i++) {
+    /* RISC-V instructions are always little-endian */
+    for (i = 0; i < 6; i++) {
         reset_vec[i] = cpu_to_le32(reset_vec[i]);
     }
+
+    /*
+     * Data words (addresses at entries 6-9) must match the firmware's data
+     * endianness.
+     */
+    if (riscv_is_32bit(harts)) {
+        for (i = 6; i < ARRAY_SIZE(reset_vec); i++) {
+            if (riscv_is_big_endian(harts)) {
+                reset_vec[i] = cpu_to_be32(reset_vec[i]);
+            } else {
+                reset_vec[i] = cpu_to_le32(reset_vec[i]);
+            }
+        }
+    } else {
+        /*
+         * For RV64, each pair of 32-bit words forms a dword. For big-endian,
+         * the hi/lo word order within each dword must be swapped since LD
+         * interprets bytes as BE.
+         */
+        for (i = 6; i < ARRAY_SIZE(reset_vec); i += 2) {
+            riscv_boot_data_dword(reset_vec + i, riscv_is_big_endian(harts));
+        }
+    }
     rom_add_blob_fixed_as("mrom.reset", reset_vec, sizeof(reset_vec),
                           rom_base, &address_space_memory);
     riscv_rom_copy_firmware_info(machine, harts,
diff --git a/include/hw/riscv/boot.h b/include/hw/riscv/boot.h
index f00b3ca122..93b9a37f03 100644
--- a/include/hw/riscv/boot.h
+++ b/include/hw/riscv/boot.h
@@ -39,6 +39,7 @@ typedef struct RISCVBootInfo {
 } RISCVBootInfo;
 
 bool riscv_is_32bit(RISCVHartArrayState *harts);
+bool riscv_is_big_endian(RISCVHartArrayState *harts);
 
 char *riscv_plic_hart_config_string(int hart_count);
 
-- 
2.34.1

[PATCH v9 5/7] target/riscv: Fix page table walk endianness for big-endian harts

[Djordje Todorovic]

The page table walker reads PTEs using address_space_ldl/ldq which use
compile-time native endianness (always LE for RISC-V). However, when a
big-endian kernel writes PTEs via normal store instructions, they are
stored in big-endian byte order. The walker then misinterprets the PTE
values, causing page faults and a hang when the kernel enables the MMU.

The RISC-V privileged specification states that implicit data memory
accesses to supervisor-level memory management data structures follow
the hart's endianness setting (MSTATUS SBE/MBE bits).

Fix both PTE reads and atomic A/D bit updates to use the explicit _le
or _be memory access variants based on the hart's runtime endianness.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 target/riscv/cpu_helper.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 39c3486ae0..4859b8dd5c 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -1418,9 +1418,13 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
         }
 
         if (riscv_cpu_mxl(env) == MXL_RV32) {
-            pte = address_space_ldl_le(cs->as, pte_addr, attrs, &res);
+            pte = riscv_cpu_data_is_big_endian(env)
+                ? address_space_ldl_be(cs->as, pte_addr, attrs, &res)
+                : address_space_ldl_le(cs->as, pte_addr, attrs, &res);
         } else {
-            pte = address_space_ldq_le(cs->as, pte_addr, attrs, &res);
+            pte = riscv_cpu_data_is_big_endian(env)
+                ? address_space_ldq_be(cs->as, pte_addr, attrs, &res)
+                : address_space_ldq_le(cs->as, pte_addr, attrs, &res);
         }
 
         if (res != MEMTX_OK) {
@@ -1619,12 +1623,24 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
         if (memory_region_is_ram(mr)) {
             target_ulong *pte_pa = qemu_map_ram_ptr(mr->ram_block, addr1);
             target_ulong old_pte;
+            bool be = riscv_cpu_data_is_big_endian(env);
             if (riscv_cpu_sxl(env) == MXL_RV32) {
-                old_pte = qatomic_cmpxchg((uint32_t *)pte_pa, cpu_to_le32(pte), cpu_to_le32(updated_pte));
-                old_pte = le32_to_cpu(old_pte);
+                uint32_t cmp = be ? cpu_to_be32(pte)
+                                  : cpu_to_le32(pte);
+                uint32_t val = be ? cpu_to_be32(updated_pte)
+                                  : cpu_to_le32(updated_pte);
+                old_pte = qatomic_cmpxchg((uint32_t *)pte_pa,
+                                          cmp, val);
+                old_pte = be ? be32_to_cpu(old_pte)
+                             : le32_to_cpu(old_pte);
             } else {
-                old_pte = qatomic_cmpxchg(pte_pa, cpu_to_le64(pte), cpu_to_le64(updated_pte));
-                old_pte = le64_to_cpu(old_pte);
+                target_ulong cmp = be ? cpu_to_be64(pte)
+                                      : cpu_to_le64(pte);
+                target_ulong val = be ? cpu_to_be64(updated_pte)
+                                      : cpu_to_le64(updated_pte);
+                old_pte = qatomic_cmpxchg(pte_pa, cmp, val);
+                old_pte = be ? be64_to_cpu(old_pte)
+                             : le64_to_cpu(old_pte);
             }
             if (old_pte != pte) {
                 goto restart;
-- 
2.34.1

[PATCH v9 6/7] target/riscv: Expose big-endian CPU property and add documentation

[Djordje Todorovic]

Now that the full big-endian data path is in place (runtime MSTATUS
bits, boot code, and page-table walks), expose the "big-endian"
property to users via DEFINE_PROP_BOOL and document it in
docs/system/target-riscv.rst.

The property can be enabled from the command line, e.g.:

    -cpu <cpu>,big-endian=on

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
---
 docs/system/target-riscv.rst | 24 ++++++++++++++++++++++++
 target/riscv/cpu.c           |  1 +
 2 files changed, 25 insertions(+)

diff --git a/docs/system/target-riscv.rst b/docs/system/target-riscv.rst
index 3ad5d1ddaf..7798184ebe 100644
--- a/docs/system/target-riscv.rst
+++ b/docs/system/target-riscv.rst
@@ -95,3 +95,27 @@ the images they need.
 * ``-bios <file>``
 
 Tells QEMU to load the specified file as the firmware.
+
+RISC-V CPU endianness
+---------------------
+
+The RISC-V ISA specifies that instruction fetches are always little-endian,
+while data accesses can be either little-endian or big-endian under control
+of the MSTATUS ``MBE``/``SBE``/``UBE`` bits (see section 3.1.6.5, "Memory
+Endianness", in the RISC-V Privileged Specification).
+
+QEMU implements the full data-endianness behaviour described by those bits.
+In addition, the RISC-V CPU object exposes a ``big-endian`` boolean property
+which models a big-endian-only hardware implementation, where the
+``MBE``/``SBE``/``UBE`` bits are hardwired to 1. When the property is set,
+the CPU is reset with all three bits initialised to 1, so the guest starts
+executing in big-endian data mode from the reset vector. The property is a
+static, per-CPU hardware configuration option and is not meant to be toggled
+at runtime.
+
+The property can be enabled from the command line, for example::
+
+    -cpu <cpu>,big-endian=on
+
+No upstream CPU model currently defaults to big-endian; the property is
+provided so that big-endian-only RISC-V CPU variants can be modelled.
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index ae75019186..f1fff92d4b 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -2657,6 +2657,7 @@ RISCVCPUImpliedExtsRule *riscv_multi_ext_implied_rules[] = {
 
 static const Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
+    DEFINE_PROP_BOOL("big-endian", RISCVCPU, cfg.big_endian, false),
 
     {.name = "pmu-mask", .info = &prop_pmu_mask},
     {.name = "pmu-num", .info = &prop_pmu_num}, /* Deprecated */
-- 
2.34.1

[PATCH v9 7/7] target/riscv: Add endianness test for RISC-V BE

[Djordje Todorovic]

Add functional test for RISC-V big-endian.

Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 tests/functional/riscv64/meson.build        |  1 +
 tests/functional/riscv64/test_endianness.py | 57 +++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 tests/functional/riscv64/test_endianness.py

diff --git a/tests/functional/riscv64/meson.build b/tests/functional/riscv64/meson.build
index b996c89d7d..5871211e89 100644
--- a/tests/functional/riscv64/meson.build
+++ b/tests/functional/riscv64/meson.build
@@ -11,6 +11,7 @@ tests_riscv64_system_quick = [
 ]
 
 tests_riscv64_system_thorough = [
+  'endianness',
   'boston',
   'sifive_u',
   'tuxrun',
diff --git a/tests/functional/riscv64/test_endianness.py b/tests/functional/riscv64/test_endianness.py
new file mode 100644
index 0000000000..9e0b3b7db5
--- /dev/null
+++ b/tests/functional/riscv64/test_endianness.py
@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+#
+# Functional tests for RISC-V big-endian support
+#
+# Copyright (c) 2026 MIPS
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+from qemu_test import QemuSystemTest, Asset
+from qemu_test import wait_for_console_pattern
+
+
+class RiscvBigEndian(QemuSystemTest):
+    """
+    Tests for RISC-V runtime big-endian data support.
+
+    Uses a bare-metal RV64 ELF that detects data endianness at runtime
+    by storing a 32-bit word and reading back byte 0. Prints "ENDIAN: BE"
+    or "ENDIAN: LE" to the NS16550A UART on the virt machine.
+    """
+
+    timeout = 10
+
+    ASSET_BE_TEST = Asset(
+        'https://github.com/MIPS/linux-test-downloads/raw/main/'
+        'riscvbe-baremetal/be-test-bare-metal.elf',
+        '9ad51b675e101de65908fadbac064ed1d0564c17463715d09dd734db86ea0f58')
+
+    def _run_bare_metal(self, big_endian=False):
+        self.set_machine('virt')
+        kernel = self.ASSET_BE_TEST.fetch()
+        self.vm.add_args('-bios', 'none')
+        self.vm.add_args('-kernel', kernel)
+        if big_endian:
+            self.vm.add_args('-cpu', 'rv64,big-endian=on')
+        self.vm.set_console()
+        self.vm.launch()
+        expected = 'ENDIAN: BE' if big_endian else 'ENDIAN: LE'
+        wait_for_console_pattern(self, expected)
+
+    def test_bare_metal_littleendian(self):
+        """
+        Boot bare-metal ELF on virt with default little-endian CPU.
+        Expects "ENDIAN: LE" on UART.
+        """
+        self._run_bare_metal(big_endian=False)
+
+    def test_bare_metal_bigendian(self):
+        """
+        Boot bare-metal ELF on virt with big-endian=on CPU property.
+        Expects "ENDIAN: BE" on UART.
+        """
+        self._run_bare_metal(big_endian=True)
+
+
+if __name__ == '__main__':
+    QemuSystemTest.main()
-- 
2.34.1

Re: [PATCH v9 1/7] target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks

[Chao Liu]

On Mon, May 11, 2026 at 08:38:27AM +0000, Djordje Todorovic wrote:
> Add the RISC-V privileged ISA defined bit positions for the Supervisor
> Big-Endian (SBE, bit 36) and Machine Big-Endian (MBE, bit 37) fields
> in the mstatus register. These are used alongside the existing
> MSTATUS_UBE (bit 6) to control data endianness at each privilege level.
> 
> The MSTATUS_UBE definition was already present, but SBE and MBE were
> missing.
> 
> Signed-off-by: Djordje Todorovic <djordje.todorovic@htecgroup.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Chao Liu <chao.liu.zevorn@gmail.com>

Thanks,
Chao
> ---
>  target/riscv/cpu_bits.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index b62dd82fe7..c2a3ee4bf3 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -628,6 +628,8 @@
>  #define MSTATUS_TSR         0x00400000 /* since: priv-1.10 */
>  #define MSTATUS_SPELP       0x00800000 /* zicfilp */
>  #define MSTATUS_SDT         0x01000000
> +#define MSTATUS_SBE         0x1000000000ULL
> +#define MSTATUS_MBE         0x2000000000ULL
>  #define MSTATUS_MPELP       0x020000000000 /* zicfilp */
>  #define MSTATUS_GVA         0x4000000000ULL
>  #define MSTATUS_MPV         0x8000000000ULL
> -- 
> 2.34.1

Re: [PATCH v9 0/7] Add RISC-V big-endian target support

[Djordje Todorovic]

Hi all,

I am wondering, if there is any comment on v9. :)

Thanks a lot!
Djordje


On 5/11/26 10:38, Djordje Todorovic wrote:
> Rebase on top of master.
>
> Djordje Todorovic (7):
>    target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
>    target/riscv: Add big-endian CPU configuration field and reset logic
>    target/riscv: Implement runtime data endianness via MSTATUS bits
>    hw/riscv: Make boot code endianness-aware at runtime
>    target/riscv: Fix page table walk endianness for big-endian harts
>    target/riscv: Expose big-endian CPU property and add documentation
>    target/riscv: Add endianness test for RISC-V BE
>
>   docs/system/target-riscv.rst                  | 24 ++++++
>   hw/riscv/boot.c                               | 81 ++++++++++++++++---
>   include/hw/riscv/boot.h                       |  1 +
>   target/riscv/cpu.c                            | 11 +--
>   target/riscv/cpu.h                            | 23 ++++++
>   target/riscv/cpu_bits.h                       |  2 +
>   target/riscv/cpu_cfg_fields.h.inc             |  1 +
>   target/riscv/cpu_helper.c                     | 28 +++++--
>   target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
>   target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
>   target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
>   target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
>   target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
>   target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
>   target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
>   target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
>   target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
>   target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
>   target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
>   target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
>   target/riscv/internals.h                      |  9 +--
>   target/riscv/tcg/tcg-cpu.c                    |  3 +
>   target/riscv/translate.c                      | 22 ++---
>   tests/functional/riscv64/meson.build          |  1 +
>   tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
>   25 files changed, 251 insertions(+), 80 deletions(-)
>   create mode 100644 tests/functional/riscv64/test_endianness.py
>

Re: [PATCH v9 0/7] Add RISC-V big-endian target support

[Michael S. Tsirkin]

On Mon, May 11, 2026 at 08:38:26AM +0000, Djordje Todorovic wrote:
> Rebase on top of master.

is Linux going to support this, ever? given this history:

https://lore.kernel.org/lkml/CAHk-%3DwgYcOiFvsJzFb%2BHfB4n6Wj6zM5H5EghUMfpXSCzyQVSfA@mail.gmail.com/t/#mce138059dc56014643bbda330810183031ef5c06

pls include a cover letter explaining why we should bother with this.


> Djordje Todorovic (7):
>   target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
>   target/riscv: Add big-endian CPU configuration field and reset logic
>   target/riscv: Implement runtime data endianness via MSTATUS bits
>   hw/riscv: Make boot code endianness-aware at runtime
>   target/riscv: Fix page table walk endianness for big-endian harts
>   target/riscv: Expose big-endian CPU property and add documentation
>   target/riscv: Add endianness test for RISC-V BE
> 
>  docs/system/target-riscv.rst                  | 24 ++++++
>  hw/riscv/boot.c                               | 81 ++++++++++++++++---
>  include/hw/riscv/boot.h                       |  1 +
>  target/riscv/cpu.c                            | 11 +--
>  target/riscv/cpu.h                            | 23 ++++++
>  target/riscv/cpu_bits.h                       |  2 +
>  target/riscv/cpu_cfg_fields.h.inc             |  1 +
>  target/riscv/cpu_helper.c                     | 28 +++++--
>  target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
>  target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
>  target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
>  target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
>  target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
>  target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
>  target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
>  target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
>  target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
>  target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
>  target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
>  target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
>  target/riscv/internals.h                      |  9 +--
>  target/riscv/tcg/tcg-cpu.c                    |  3 +
>  target/riscv/translate.c                      | 22 ++---
>  tests/functional/riscv64/meson.build          |  1 +
>  tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
>  25 files changed, 251 insertions(+), 80 deletions(-)
>  create mode 100644 tests/functional/riscv64/test_endianness.py
> 
> -- 
> 2.34.1

Re: [PATCH v9 0/7] Add RISC-V big-endian target support

[Philippe Mathieu-Daudé]

On 20/5/26 16:08, Djordje Todorovic wrote:
> Hi all,
> 
> I am wondering, if there is any comment on v9. :)
> 
> Thanks a lot!
> Djordje
> 
> 
> On 5/11/26 10:38, Djordje Todorovic wrote:
>> Rebase on top of master.

More than a "rebase" comment I was hoping to read what was the
conclusion on previous versions about wired endianness bits.

>>
>> Djordje Todorovic (7):
>>     target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
>>     target/riscv: Add big-endian CPU configuration field and reset logic
>>     target/riscv: Implement runtime data endianness via MSTATUS bits
>>     hw/riscv: Make boot code endianness-aware at runtime
>>     target/riscv: Fix page table walk endianness for big-endian harts
>>     target/riscv: Expose big-endian CPU property and add documentation
>>     target/riscv: Add endianness test for RISC-V BE
>>
>>    docs/system/target-riscv.rst                  | 24 ++++++
>>    hw/riscv/boot.c                               | 81 ++++++++++++++++---
>>    include/hw/riscv/boot.h                       |  1 +
>>    target/riscv/cpu.c                            | 11 +--
>>    target/riscv/cpu.h                            | 23 ++++++
>>    target/riscv/cpu_bits.h                       |  2 +
>>    target/riscv/cpu_cfg_fields.h.inc             |  1 +
>>    target/riscv/cpu_helper.c                     | 28 +++++--
>>    target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
>>    target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
>>    target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
>>    target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
>>    target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
>>    target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
>>    target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
>>    target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
>>    target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
>>    target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
>>    target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
>>    target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
>>    target/riscv/internals.h                      |  9 +--
>>    target/riscv/tcg/tcg-cpu.c                    |  3 +
>>    target/riscv/translate.c                      | 22 ++---
>>    tests/functional/riscv64/meson.build          |  1 +
>>    tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
>>    25 files changed, 251 insertions(+), 80 deletions(-)
>>    create mode 100644 tests/functional/riscv64/test_endianness.py
>>

Re: [PATCH v9 0/7] Add RISC-V big-endian target support

[Philippe Mathieu-Daudé]

On 20/5/26 16:12, Michael S. Tsirkin wrote:
> On Mon, May 11, 2026 at 08:38:26AM +0000, Djordje Todorovic wrote:
>> Rebase on top of master.
> 
> is Linux going to support this, ever? given this history:
> 
> https://lore.kernel.org/lkml/CAHk-%3DwgYcOiFvsJzFb%2BHfB4n6Wj6zM5H5EghUMfpXSCzyQVSfA@mail.gmail.com/t/#mce138059dc56014643bbda330810183031ef5c06
> 
> pls include a cover letter explaining why we should bother with this.

We can run any kind of guests, not limiting ourselves to Linux kernel.

> 
>> Djordje Todorovic (7):
>>    target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
>>    target/riscv: Add big-endian CPU configuration field and reset logic
>>    target/riscv: Implement runtime data endianness via MSTATUS bits
>>    hw/riscv: Make boot code endianness-aware at runtime
>>    target/riscv: Fix page table walk endianness for big-endian harts
>>    target/riscv: Expose big-endian CPU property and add documentation
>>    target/riscv: Add endianness test for RISC-V BE
>>
>>   docs/system/target-riscv.rst                  | 24 ++++++
>>   hw/riscv/boot.c                               | 81 ++++++++++++++++---
>>   include/hw/riscv/boot.h                       |  1 +
>>   target/riscv/cpu.c                            | 11 +--
>>   target/riscv/cpu.h                            | 23 ++++++
>>   target/riscv/cpu_bits.h                       |  2 +
>>   target/riscv/cpu_cfg_fields.h.inc             |  1 +
>>   target/riscv/cpu_helper.c                     | 28 +++++--
>>   target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
>>   target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
>>   target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
>>   target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
>>   target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
>>   target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
>>   target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
>>   target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
>>   target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
>>   target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
>>   target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
>>   target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
>>   target/riscv/internals.h                      |  9 +--
>>   target/riscv/tcg/tcg-cpu.c                    |  3 +
>>   target/riscv/translate.c                      | 22 ++---
>>   tests/functional/riscv64/meson.build          |  1 +
>>   tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
>>   25 files changed, 251 insertions(+), 80 deletions(-)
>>   create mode 100644 tests/functional/riscv64/test_endianness.py
>>
>> -- 
>> 2.34.1
> 

Re: [PATCH v9 0/7] Add RISC-V big-endian target support

[Djordje Todorovic]

On 5/20/26 19:19, Philippe Mathieu-Daudé wrote:
> CAUTION: This email originated from outside of the organization. Do 
> not click links or open attachments unless you recognize the sender 
> and know the content is safe.
>
>
> On 20/5/26 16:08, Djordje Todorovic wrote:
>> Hi all,
>>
>> I am wondering, if there is any comment on v9. :)
>>
>> Thanks a lot!
>> Djordje
>>
>>
>> On 5/11/26 10:38, Djordje Todorovic wrote:
>>> Rebase on top of master.
>
> More than a "rebase" comment I was hoping to read what was the
> conclusion on previous versions about wired endianness bits.
>
Yes, sorry, I should have made that clearer in the cover letter.

This was partially addressed in v7 by making `big-endian` a static CPU
configuration option rather than a runtime switch. In v10 I made the
intended model explicit: this series models fixed-endian harts, not a
mixed-endian implementation where software can toggle MBE/SBE/UBE at
runtime.

The reset value of MBE/SBE/UBE is selected from the CPU configuration, and
the bits remain outside the mstatus/mstatush/sstatus writable masks, so
they are effectively hardwired to 0 for the default little-endian CPUs and
to 1 when `big-endian=on`.

I also documented this in the patches and will mention it explicitly in the
v10 cover letter.

>>>
>>> Djordje Todorovic (7):
>>>     target/riscv: Define MSTATUS_SBE and MSTATUS_MBE bit masks
>>>     target/riscv: Add big-endian CPU configuration field and reset 
>>> logic
>>>     target/riscv: Implement runtime data endianness via MSTATUS bits
>>>     hw/riscv: Make boot code endianness-aware at runtime
>>>     target/riscv: Fix page table walk endianness for big-endian harts
>>>     target/riscv: Expose big-endian CPU property and add documentation
>>>     target/riscv: Add endianness test for RISC-V BE
>>>
>>>    docs/system/target-riscv.rst                  | 24 ++++++
>>>    hw/riscv/boot.c                               | 81 
>>> ++++++++++++++++---
>>>    include/hw/riscv/boot.h                       |  1 +
>>>    target/riscv/cpu.c                            | 11 +--
>>>    target/riscv/cpu.h                            | 23 ++++++
>>>    target/riscv/cpu_bits.h                       |  2 +
>>>    target/riscv/cpu_cfg_fields.h.inc             |  1 +
>>>    target/riscv/cpu_helper.c                     | 28 +++++--
>>>    target/riscv/insn_trans/trans_rva.c.inc       |  4 +-
>>>    target/riscv/insn_trans/trans_rvd.c.inc       |  4 +-
>>>    target/riscv/insn_trans/trans_rvf.c.inc       |  4 +-
>>>    target/riscv/insn_trans/trans_rvi.c.inc       |  8 +-
>>>    target/riscv/insn_trans/trans_rvzacas.c.inc   |  4 +-
>>>    target/riscv/insn_trans/trans_rvzalasr.c.inc  |  4 +-
>>>    target/riscv/insn_trans/trans_rvzce.c.inc     |  4 +-
>>>    target/riscv/insn_trans/trans_rvzfh.c.inc     |  4 +-
>>>    target/riscv/insn_trans/trans_rvzicfiss.c.inc |  4 +-
>>>    target/riscv/insn_trans/trans_xmips.c.inc     |  8 +-
>>>    target/riscv/insn_trans/trans_xthead.c.inc    | 16 ++--
>>>    target/riscv/insn_trans/trans_zilsd.c.inc     |  4 +-
>>>    target/riscv/internals.h                      |  9 +--
>>>    target/riscv/tcg/tcg-cpu.c                    |  3 +
>>>    target/riscv/translate.c                      | 22 ++---
>>>    tests/functional/riscv64/meson.build          |  1 +
>>>    tests/functional/riscv64/test_endianness.py   | 57 +++++++++++++
>>>    25 files changed, 251 insertions(+), 80 deletions(-)
>>>    create mode 100644 tests/functional/riscv64/test_endianness.py
>>>
>