target/riscv: implement Zicboz extension

The RISC-V base cache management operation (CBO) ISA extension has been
ratified. It defines three extensions: Cache-Block Management, Cache-Block
Prefetch and Cache-Block Zero. More information about the spec can be
found at [1].

Let's start by implementing the Cache-Block Zero extension, Zicboz. It
uses the cbo.zero instruction that, as with all CBO instructions that
will be added later, needs to be implemented in an overlap group with
the LQ instruction due to overlapping patterns.

cbo.zero throws a Illegal Instruction/Virtual Instruction exception
depending on CSR state. This is also the case for the remaining cbo
instructions we're going to add next, so create a check_zicbo_envcfg()
that will be used by all Zicbo[mz] instructions.

[1] https://github.com/riscv/riscv-CMOs/blob/master/specifications/cmobase-v1.0.1.pdf

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Co-developed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Signed-off-by: Christoph Muellner <cmuellner@linux.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Message-ID: <20230224132536.552293-3-dbarboza@ventanamicro.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

target/riscv/cpu.c

@@ -75,6 +75,7 @@ struct isa_ext_data {
 static const struct isa_ext_data isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(h, false, PRIV_VERSION_1_12_0, ext_h),
     ISA_EXT_DATA_ENTRY(v, false, PRIV_VERSION_1_10_0, ext_v),
+    ISA_EXT_DATA_ENTRY(zicboz, true, PRIV_VERSION_1_12_0, ext_icboz),
     ISA_EXT_DATA_ENTRY(zicond, true, PRIV_VERSION_1_12_0, ext_zicond),
     ISA_EXT_DATA_ENTRY(zicsr, true, PRIV_VERSION_1_10_0, ext_icsr),
     ISA_EXT_DATA_ENTRY(zifencei, true, PRIV_VERSION_1_10_0, ext_ifencei),
@@ -1167,6 +1168,9 @@ static Property riscv_cpu_extensions[] = {
     DEFINE_PROP_BOOL("zhinx", RISCVCPU, cfg.ext_zhinx, false),
     DEFINE_PROP_BOOL("zhinxmin", RISCVCPU, cfg.ext_zhinxmin, false),
 
+    DEFINE_PROP_BOOL("zicboz", RISCVCPU, cfg.ext_icboz, true),
+    DEFINE_PROP_UINT16("cboz_blocksize", RISCVCPU, cfg.cboz_blocksize, 64),
+
     DEFINE_PROP_BOOL("zmmul", RISCVCPU, cfg.ext_zmmul, false),
 
     /* Vendor-specific custom extensions */

target/riscv/cpu.h

@@ -434,6 +434,7 @@ struct RISCVCPUConfig {
     bool ext_zkt;
     bool ext_ifencei;
     bool ext_icsr;
+    bool ext_icboz;
     bool ext_zicond;
     bool ext_zihintpause;
     bool ext_smstateen;
@@ -486,6 +487,7 @@ struct RISCVCPUConfig {
     char *vext_spec;
     uint16_t vlen;
     uint16_t elen;
+    uint16_t cboz_blocksize;
     bool mmu;
     bool pmp;
     bool epmp;

target/riscv/helper.h

@@ -97,6 +97,9 @@ DEF_HELPER_FLAGS_2(fcvt_h_l, TCG_CALL_NO_RWG, i64, env, tl)
 DEF_HELPER_FLAGS_2(fcvt_h_lu, TCG_CALL_NO_RWG, i64, env, tl)
 DEF_HELPER_FLAGS_2(fclass_h, TCG_CALL_NO_RWG_SE, tl, env, i64)
 
+/* Cache-block operations */
+DEF_HELPER_2(cbo_zero, void, env, tl)
+
 /* Special functions */
 DEF_HELPER_2(csrr, tl, env, int)
 DEF_HELPER_3(csrw, void, env, int, tl)

target/riscv/insn32.decode

@@ -179,7 +179,15 @@ sraw     0100000 .....  ..... 101 ..... 0111011 @r
 
 # *** RV128I Base Instruction Set (in addition to RV64I) ***
 ldu      ............   ..... 111 ..... 0000011 @i
-lq       ............   ..... 010 ..... 0001111 @i
+{
+  [
+    # *** RV32 Zicboz Standard Extension ***
+    cbo_zero   0000000 00100 ..... 010 00000 0001111 @sfence_vm
+  ]
+
+  # *** RVI128 lq ***
+  lq       ............   ..... 010 ..... 0001111 @i
+}
 sq       ............   ..... 100 ..... 0100011 @s
 addid    ............  .....  000 ..... 1011011 @i
 sllid    000000 ......  ..... 001 ..... 1011011 @sh6

target/riscv/insn_trans/trans_rvzicbo.c.inc

@@ -0,0 +1,30 @@
+/*
+ * RISC-V translation routines for the RISC-V CBO Extension.
+ *
+ * Copyright (c) 2021 Philipp Tomsich, philipp.tomsich@vrull.eu
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define REQUIRE_ZICBOZ(ctx) do {    \
+    if (!ctx->cfg_ptr->ext_icboz) { \
+        return false;               \
+    }                               \
+} while (0)
+
+static bool trans_cbo_zero(DisasContext *ctx, arg_cbo_zero *a)
+{
+    REQUIRE_ZICBOZ(ctx);
+    gen_helper_cbo_zero(cpu_env, cpu_gpr[a->rs1]);
+    return true;
+}

target/riscv/op_helper.c

@@ -3,6 +3,7 @@
  *
  * Copyright (c) 2016-2017 Sagar Karandikar, sagark@eecs.berkeley.edu
  * Copyright (c) 2017-2018 SiFive, Inc.
+ * Copyright (c) 2022      VRULL GmbH
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,
@@ -123,6 +124,73 @@ target_ulong helper_csrrw_i128(CPURISCVState *env, int csr,
     return int128_getlo(rv);
 }
 
+
+/*
+ * check_zicbo_envcfg
+ *
+ * Raise virtual exceptions and illegal instruction exceptions for
+ * Zicbo[mz] instructions based on the settings of [mhs]envcfg as
+ * specified in section 2.5.1 of the CMO specification.
+ */
+static void check_zicbo_envcfg(CPURISCVState *env, target_ulong envbits,
+                                uintptr_t ra)
+{
+#ifndef CONFIG_USER_ONLY
+    if ((env->priv < PRV_M) && !get_field(env->menvcfg, envbits)) {
+        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, ra);
+    }
+
+    if (riscv_cpu_virt_enabled(env) &&
+        (((env->priv < PRV_H) && !get_field(env->henvcfg, envbits)) ||
+         ((env->priv < PRV_S) && !get_field(env->senvcfg, envbits)))) {
+        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, ra);
+    }
+
+    if ((env->priv < PRV_S) && !get_field(env->senvcfg, envbits)) {
+        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, ra);
+    }
+#endif
+}
+
+void helper_cbo_zero(CPURISCVState *env, target_ulong address)
+{
+    RISCVCPU *cpu = env_archcpu(env);
+    uint16_t cbozlen = cpu->cfg.cboz_blocksize;
+    int mmu_idx = cpu_mmu_index(env, false);
+    uintptr_t ra = GETPC();
+    void *mem;
+
+    check_zicbo_envcfg(env, MENVCFG_CBZE, ra);
+
+    /* Mask off low-bits to align-down to the cache-block. */
+    address &= ~(cbozlen - 1);
+
+    /*
+     * cbo.zero requires MMU_DATA_STORE access. Do a probe_write()
+     * to raise any exceptions, including PMP.
+     */
+    mem = probe_write(env, address, cbozlen, mmu_idx, ra);
+
+    if (likely(mem)) {
+        memset(mem, 0, cbozlen);
+    } else {
+        /*
+         * This means that we're dealing with an I/O page. Section 4.2
+         * of cmobase v1.0.1 says:
+         *
+         * "Cache-block zero instructions store zeros independently
+         * of whether data from the underlying memory locations are
+         * cacheable."
+         *
+         * Write zeros in address + cbozlen regardless of not being
+         * a RAM page.
+         */
+        for (int i = 0; i < cbozlen; i++) {
+            cpu_stb_mmuidx_ra(env, address + i, 0, mmu_idx, ra);
+        }
+    }
+}
+
 #ifndef CONFIG_USER_ONLY
 
 target_ulong helper_sret(CPURISCVState *env)

target/riscv/translate.c

@@ -1105,6 +1105,7 @@ static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc)
 #include "insn_trans/trans_rvb.c.inc"
 #include "insn_trans/trans_rvzicond.c.inc"
 #include "insn_trans/trans_rvzawrs.c.inc"
+#include "insn_trans/trans_rvzicbo.c.inc"
 #include "insn_trans/trans_rvzfh.c.inc"
 #include "insn_trans/trans_rvk.c.inc"
 #include "insn_trans/trans_privileged.c.inc"