target/riscv: do not enable all named features by default

Commit 3b8022269c added the capability of named features/profile
extensions to be added in riscv,isa. To do that we had to assign priv
versions for each one of them in isa_edata_arr[]. But this resulted in a
side-effect: vendor CPUs that aren't running priv_version_latest started
to experience warnings for these profile extensions [1]:

  | $ qemu-system-riscv32  -M sifive_e
  | qemu-system-riscv32: warning: disabling zic64b extension for hart
0x00000000 because privilege spec version does not match
  | qemu-system-riscv32: warning: disabling ziccamoa extension for
hart 0x00000000 because privilege spec version does not match

This is benign as far as the CPU behavior is concerned since disabling
both extensions is a no-op (aside from riscv,isa). But the warnings are
unpleasant to deal with, especially because we're sending user warnings
for extensions that users can't enable/disable.

Instead of enabling all named features all the time, separate them by
priv version. During finalize() time, after we decided which
priv_version the CPU is running, enable/disable all the named extensions
based on the priv spec chosen. This will be enough for a bug fix, but as
a future work we should look into how we can name these extensions in a
way that we don't need an explicit ext_name => priv_ver as we're doing
here.

The named extensions being added in isa_edata_arr[] that will be
enabled/disabled based solely on priv version can be removed from
riscv_cpu_named_features[]. 'zic64b' is an extension that can be
disabled based on block sizes so it'll retain its own flag and entry.

[1] https://lists.gnu.org/archive/html/qemu-devel/2024-03/msg02592.html

Reported-by: Clément Chigot <chigot@adacore.com>
Fixes: 3b8022269c ("target/riscv: add riscv,isa to named features")
Suggested-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Clément Chigot <chigot@adacore.com>
Message-ID: <20240312203214.350980-1-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index c160b9216b238b16dacea2aa3357021b13c24e50..36e3e5fdaf513d90fcbddbc37fd71fc35a71d1d1 100644 (file)
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -102,10 +102,10 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zicbom, PRIV_VERSION_1_12_0, ext_zicbom),
     ISA_EXT_DATA_ENTRY(zicbop, PRIV_VERSION_1_12_0, ext_zicbop),
     ISA_EXT_DATA_ENTRY(zicboz, PRIV_VERSION_1_12_0, ext_zicboz),
-    ISA_EXT_DATA_ENTRY(ziccamoa, PRIV_VERSION_1_11_0, ext_always_enabled),
-    ISA_EXT_DATA_ENTRY(ziccif, PRIV_VERSION_1_11_0, ext_always_enabled),
-    ISA_EXT_DATA_ENTRY(zicclsm, PRIV_VERSION_1_11_0, ext_always_enabled),
-    ISA_EXT_DATA_ENTRY(ziccrse, PRIV_VERSION_1_11_0, ext_always_enabled),
+    ISA_EXT_DATA_ENTRY(ziccamoa, PRIV_VERSION_1_11_0, has_priv_1_11),
+    ISA_EXT_DATA_ENTRY(ziccif, PRIV_VERSION_1_11_0, has_priv_1_11),
+    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(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),
@@ -114,7 +114,7 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zihintpause, PRIV_VERSION_1_10_0, ext_zihintpause),
     ISA_EXT_DATA_ENTRY(zihpm, PRIV_VERSION_1_12_0, ext_zihpm),
     ISA_EXT_DATA_ENTRY(zmmul, PRIV_VERSION_1_12_0, ext_zmmul),
-    ISA_EXT_DATA_ENTRY(za64rs, PRIV_VERSION_1_12_0, ext_always_enabled),
+    ISA_EXT_DATA_ENTRY(za64rs, PRIV_VERSION_1_12_0, has_priv_1_11),
     ISA_EXT_DATA_ENTRY(zaamo, PRIV_VERSION_1_12_0, ext_zaamo),
     ISA_EXT_DATA_ENTRY(zacas, PRIV_VERSION_1_12_0, ext_zacas),
     ISA_EXT_DATA_ENTRY(zalrsc, PRIV_VERSION_1_12_0, ext_zalrsc),
@@ -179,12 +179,12 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(smepmp, PRIV_VERSION_1_12_0, ext_smepmp),
     ISA_EXT_DATA_ENTRY(smstateen, PRIV_VERSION_1_12_0, ext_smstateen),
     ISA_EXT_DATA_ENTRY(ssaia, PRIV_VERSION_1_12_0, ext_ssaia),
-    ISA_EXT_DATA_ENTRY(ssccptr, PRIV_VERSION_1_11_0, ext_always_enabled),
+    ISA_EXT_DATA_ENTRY(ssccptr, PRIV_VERSION_1_11_0, has_priv_1_11),
     ISA_EXT_DATA_ENTRY(sscofpmf, PRIV_VERSION_1_12_0, ext_sscofpmf),
-    ISA_EXT_DATA_ENTRY(sscounterenw, PRIV_VERSION_1_12_0, ext_always_enabled),
+    ISA_EXT_DATA_ENTRY(sscounterenw, PRIV_VERSION_1_12_0, has_priv_1_12),
     ISA_EXT_DATA_ENTRY(sstc, PRIV_VERSION_1_12_0, ext_sstc),
-    ISA_EXT_DATA_ENTRY(sstvala, PRIV_VERSION_1_12_0, ext_always_enabled),
-    ISA_EXT_DATA_ENTRY(sstvecd, PRIV_VERSION_1_12_0, ext_always_enabled),
+    ISA_EXT_DATA_ENTRY(sstvala, PRIV_VERSION_1_12_0, has_priv_1_12),
+    ISA_EXT_DATA_ENTRY(sstvecd, PRIV_VERSION_1_12_0, has_priv_1_12),
     ISA_EXT_DATA_ENTRY(svade, PRIV_VERSION_1_11_0, ext_svade),
     ISA_EXT_DATA_ENTRY(svadu, PRIV_VERSION_1_12_0, ext_svadu),
     ISA_EXT_DATA_ENTRY(svinval, PRIV_VERSION_1_12_0, ext_svinval),
@@ -1575,11 +1575,6 @@ const RISCVCPUMultiExtConfig riscv_cpu_experimental_exts[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
-#define ALWAYS_ENABLED_FEATURE(_name) \
-    {.name = _name, \
-     .offset = CPU_CFG_OFFSET(ext_always_enabled), \
-     .enabled = true}
-
 /*
  * 'Named features' is the name we give to extensions that we
  * don't want to expose to users. They are either immutable
@@ -1590,23 +1585,6 @@ const RISCVCPUMultiExtConfig riscv_cpu_experimental_exts[] = {
 const RISCVCPUMultiExtConfig riscv_cpu_named_features[] = {
     MULTI_EXT_CFG_BOOL("zic64b", ext_zic64b, true),
 
-    /*
-     * cache-related extensions that are always enabled
-     * in TCG since QEMU RISC-V does not have a cache
-     * model.
-     */
-    ALWAYS_ENABLED_FEATURE("za64rs"),
-    ALWAYS_ENABLED_FEATURE("ziccif"),
-    ALWAYS_ENABLED_FEATURE("ziccrse"),
-    ALWAYS_ENABLED_FEATURE("ziccamoa"),
-    ALWAYS_ENABLED_FEATURE("zicclsm"),
-    ALWAYS_ENABLED_FEATURE("ssccptr"),
-
-    /* Other named features that TCG always implements */
-    ALWAYS_ENABLED_FEATURE("sstvecd"),
-    ALWAYS_ENABLED_FEATURE("sstvala"),
-    ALWAYS_ENABLED_FEATURE("sscounterenw"),
-
     DEFINE_PROP_END_OF_LIST(),
 };
 

diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
index 2040b90da0da8f600bca0d6cf461939852de62e1..cb750154bd7b58e6d74b812286b448b62698cfce 100644 (file)
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -130,10 +130,12 @@ struct RISCVCPUConfig {
     bool ext_zic64b;
 
     /*
-     * Always 'true' boolean for named features
-     * TCG always implement/can't be disabled.
+     * Always 'true' booleans for named features
+     * TCG always implement/can't be user disabled,
+     * based on spec version.
      */
-    bool ext_always_enabled;
+    bool has_priv_1_12;
+    bool has_priv_1_11;
 
     /* Vendor-specific custom extensions */
     bool ext_xtheadba;

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index ab6db817dbdb5bf97b80f393fd900ee9fca07761..63192ef54f3de92d00c2d217a62b577718b30f4b 100644 (file)
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -315,9 +315,19 @@ static void riscv_cpu_disable_priv_spec_isa_exts(RISCVCPU *cpu)
 
 static void riscv_cpu_update_named_features(RISCVCPU *cpu)
 {
+    if (cpu->env.priv_ver >= PRIV_VERSION_1_11_0) {
+        cpu->cfg.has_priv_1_11 = true;
+    }
+
+    if (cpu->env.priv_ver >= PRIV_VERSION_1_12_0) {
+        cpu->cfg.has_priv_1_12 = true;
+    }
+
+    /* zic64b is 1.12 or later */
     cpu->cfg.ext_zic64b = cpu->cfg.cbom_blocksize == 64 &&
                           cpu->cfg.cbop_blocksize == 64 &&
-                          cpu->cfg.cboz_blocksize == 64;
+                          cpu->cfg.cboz_blocksize == 64 &&
+                          cpu->cfg.has_priv_1_12;
 }
 
 static void riscv_cpu_validate_g(RISCVCPU *cpu)
@@ -1316,8 +1326,6 @@ static void riscv_tcg_cpu_instance_init(CPUState *cs)
     RISCVCPU *cpu = RISCV_CPU(cs);
     Object *obj = OBJECT(cpu);
 
-    cpu->cfg.ext_always_enabled = true;
-
     misa_ext_user_opts = g_hash_table_new(NULL, g_direct_equal);
     multi_ext_user_opts = g_hash_table_new(NULL, g_direct_equal);
     riscv_cpu_add_user_properties(obj);