zicfiss [1] riscv cpu extension enables backward control flow integrity.

This patch sets up space for zicfiss extension in cpuconfig. And imple-
ments dependency on A, zicsr, zimop and zcmop extensions.

[1] - https://github.com/riscv/riscv-cfi

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Co-developed-by: Jim Shu <jim.shu@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/cpu.c         |  1 +
 target/riscv/cpu_cfg.h     |  1 +
 target/riscv/tcg/tcg-cpu.c | 23 +++++++++++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 135559fc95..09e0b7e0e5 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -107,6 +107,7 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zicclsm, PRIV_VERSION_1_11_0, has_priv_1_11),
     ISA_EXT_DATA_ENTRY(ziccrse, PRIV_VERSION_1_11_0, has_priv_1_11),
     ISA_EXT_DATA_ENTRY(zicfilp, PRIV_VERSION_1_12_0, ext_zicfilp),
+    ISA_EXT_DATA_ENTRY(zicfiss, PRIV_VERSION_1_13_0, ext_zicfiss),
     ISA_EXT_DATA_ENTRY(zicond, PRIV_VERSION_1_12_0, ext_zicond),
     ISA_EXT_DATA_ENTRY(zicntr, PRIV_VERSION_1_12_0, ext_zicntr),
     ISA_EXT_DATA_ENTRY(zicsr, PRIV_VERSION_1_10_0, ext_zicsr),
diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
index fe7ad85b66..59d6fc445d 100644
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -68,6 +68,7 @@ struct RISCVCPUConfig {
     bool ext_zicbop;
     bool ext_zicboz;
     bool ext_zicfilp;
+    bool ext_zicfiss;
     bool ext_zicond;
     bool ext_zihintntl;
     bool ext_zihintpause;
diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 963c1c604a..6c0c319499 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -618,6 +618,29 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
         cpu->cfg.ext_zihpm = false;
     }
 
+    if (cpu->cfg.ext_zicfiss) {
+        if (!cpu->cfg.ext_zicsr) {
+            error_setg(errp, "zicfiss extension requires zicsr extension");
+            return;
+        }
+        if (!riscv_has_ext(env, RVA)) {
+            error_setg(errp, "zicfiss extension requires A extension");
+            return;
+        }
+        if (!riscv_has_ext(env, RVS)) {
+            error_setg(errp, "zicfiss extension requires S");
+            return;
+        }
+        if (!cpu->cfg.ext_zimop) {
+            error_setg(errp, "zicfiss extension requires zimop extension");
+            return;
+        }
+        if (cpu->cfg.ext_zca && !cpu->cfg.ext_zcmop) {
+            error_setg(errp, "zicfiss with zca requires zcmop extension");
+            return;
+        }
+    }
+
     if (!cpu->cfg.ext_zihpm) {
         cpu->cfg.pmu_mask = 0;
         cpu->pmu_avail_ctrs = 0;
-- 
2.45.0