[PATCH v2 00/11] enable write_misa() and RISCV_FEATURE_* cleanups

[PATCH v2 00/11] enable write_misa() and RISCV_FEATURE_* cleanups

[Daniel Henrique Barboza]

Hi,

This new version contains suggestions made by Weiwei Li in v1. Most
notable change is patch 4 from v1, moving up to patch 2 now,  to allow
the riscv_cpu_cfg() helper to be used in the MISA CSR patch.


Changes in v2:
- former patch 4 moved to patch 2
- patch 3 (former 2):
  - use riscv_cpu_cfg()
- patch 9:
  - remove the uneeded RISCVCPUConfig and access mmu via
    cpu_cfg->cfg.mmu
- v1 link: https://lists.gnu.org/archive/html/qemu-devel/2023-02/msg02780.html

Daniel Henrique Barboza (11):
  target/riscv: do not mask unsupported QEMU extensions in write_misa()
  target/riscv: introduce riscv_cpu_cfg()
  target/riscv: allow users to actually write the MISA CSR
  target/riscv: remove RISCV_FEATURE_MISA
  target/riscv: remove RISCV_FEATURE_DEBUG
  target/riscv/cpu.c: error out if EPMP is enabled without PMP
  target/riscv: remove RISCV_FEATURE_EPMP
  target/riscv: remove RISCV_FEATURE_PMP
  hw/riscv/virt.c: do not use RISCV_FEATURE_MMU in
    create_fdt_socket_cpus()
  target/riscv: remove RISCV_FEATURE_MMU
  target/riscv/cpu: remove CPUArchState::features and friends

 hw/riscv/virt.c           |  7 ++++---
 target/riscv/cpu.c        | 20 +++++---------------
 target/riscv/cpu.h        | 29 ++++++-----------------------
 target/riscv/cpu_helper.c |  6 +++---
 target/riscv/csr.c        | 15 ++++++---------
 target/riscv/machine.c    | 11 ++++-------
 target/riscv/monitor.c    |  2 +-
 target/riscv/op_helper.c  |  2 +-
 target/riscv/pmp.c        |  8 ++++----
 9 files changed, 34 insertions(+), 66 deletions(-)

-- 
2.39.1

[PATCH v2 01/11] target/riscv: do not mask unsupported QEMU extensions in write_misa()

[Daniel Henrique Barboza]

The masking done using env->misa_ext_mask already filters any extension
that QEMU doesn't support. If the hart supports the extension then QEMU
supports it as well.

If the masking done by env->misa_ext_mask is somehow letting unsupported
QEMU extensions pass by, misa_ext_mask itself needs to be fixed instead.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/csr.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 1b0a0c1693..e149b453da 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -1356,9 +1356,6 @@ static RISCVException write_misa(CPURISCVState *env, int csrno,
     /* Mask extensions that are not supported by this hart */
     val &= env->misa_ext_mask;
 
-    /* Mask extensions that are not supported by QEMU */
-    val &= (RVI | RVE | RVM | RVA | RVF | RVD | RVC | RVS | RVU | RVV);
-
     /* 'D' depends on 'F', so clear 'D' if 'F' is not present */
     if ((val & RVD) && !(val & RVF)) {
         val &= ~RVD;
-- 
2.39.1

[PATCH v2 02/11] target/riscv: introduce riscv_cpu_cfg()

[Daniel Henrique Barboza]

We're going to do changes that requires accessing the RISCVCPUConfig
struct from the RISCVCPU, having access only to a CPURISCVState 'env'
pointer. Add a helper to make the code easier to read.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 7128438d8e..5e4d056772 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -654,6 +654,11 @@ static inline RISCVMXL riscv_cpu_mxl(CPURISCVState *env)
 #endif
 #define riscv_cpu_mxl_bits(env) (1UL << (4 + riscv_cpu_mxl(env)))
 
+static inline RISCVCPUConfig riscv_cpu_cfg(CPURISCVState *env)
+{
+    return env_archcpu(env)->cfg;
+}
+
 #if defined(TARGET_RISCV32)
 #define cpu_recompute_xl(env)  ((void)(env), MXL_RV32)
 #else
-- 
2.39.1

[PATCH v2 03/11] target/riscv: allow users to actually write the MISA CSR

[Daniel Henrique Barboza]

At this moment, and apparently since ever, we have no way of enabling
RISCV_FEATURE_MISA. This means that all the code from write_misa(), all
the nuts and bolts that handles how to properly write this CSR, has
always been a no-op as well because write_misa() will always exit
earlier.

This seems to be benign in the majority of cases. Booting an Ubuntu
'virt' guest and logging all the calls to 'write_misa' shows that no
writes to MISA CSR was attempted. Writing MISA, i.e. enabling/disabling
RISC-V extensions after the machine is powered on, seems to be a niche
use.

There is a good chance that the code in write_misa() hasn't been
properly tested. Allowing users to write MISA can open the floodgates of
new breeds of bugs. We could instead remove most (if not all) of
write_misa() since it's never used. Well, as a hardware emulator,
dealing with crashes because a register write went wrong is what we're
here for.

Create a 'misa-w' CPU property to allow users to choose whether writes
to MISA should be allowed. The default is set to 'false' for all RISC-V
machines to keep compatibility with what we´ve been doing so far.

Read cpu->cfg.misa_w directly in write_misa(), instead of executing
riscv_set_feature(RISCV_FEATURE_MISA) in riscv_cpu_realize(), that would
simply reflect the cpu->cfg.misa_w bool value in 'env->features' and
require a riscv_feature() call to read it back.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 1 +
 target/riscv/cpu.h | 1 +
 target/riscv/csr.c | 2 +-
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 93b52b826c..69fb9e123f 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1197,6 +1197,7 @@ static void register_cpu_props(DeviceState *dev)
 
 static Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
+    DEFINE_PROP_BOOL("misa-w", RISCVCPU, cfg.misa_w, false),
 
     DEFINE_PROP_UINT32("mvendorid", RISCVCPU, cfg.mvendorid, 0),
     DEFINE_PROP_UINT64("marchid", RISCVCPU, cfg.marchid, RISCV_CPU_MARCHID),
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 5e4d056772..fe572b83e9 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -498,6 +498,7 @@ struct RISCVCPUConfig {
     bool pmp;
     bool epmp;
     bool debug;
+    bool misa_w;
 
     bool short_isa_string;
 };
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index e149b453da..e949e6248a 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -1329,7 +1329,7 @@ static RISCVException read_misa(CPURISCVState *env, int csrno,
 static RISCVException write_misa(CPURISCVState *env, int csrno,
                                  target_ulong val)
 {
-    if (!riscv_feature(env, RISCV_FEATURE_MISA)) {
+    if (!riscv_cpu_cfg(env).misa_w) {
         /* drop write to misa */
         return RISCV_EXCP_NONE;
     }
-- 
2.39.1

[PATCH v2 04/11] target/riscv: remove RISCV_FEATURE_MISA

[Daniel Henrique Barboza]

This enum is no longer used after write_misa() started reading the value
from cpu->cfg.misa_w.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index fe572b83e9..00a464c9c4 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -89,7 +89,6 @@ enum {
     RISCV_FEATURE_MMU,
     RISCV_FEATURE_PMP,
     RISCV_FEATURE_EPMP,
-    RISCV_FEATURE_MISA,
     RISCV_FEATURE_DEBUG
 };
 
-- 
2.39.1

[PATCH v2 05/11] target/riscv: remove RISCV_FEATURE_DEBUG

[Daniel Henrique Barboza]

RISCV_FEATURE_DEBUG will always follow the value defined by
cpu->cfg.debug flag. Read the flag instead.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c        | 6 +-----
 target/riscv/cpu.h        | 1 -
 target/riscv/cpu_helper.c | 2 +-
 target/riscv/csr.c        | 2 +-
 target/riscv/machine.c    | 3 +--
 5 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 69fb9e123f..272cf1a8bf 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -637,7 +637,7 @@ static void riscv_cpu_reset_hold(Object *obj)
     set_default_nan_mode(1, &env->fp_status);
 
 #ifndef CONFIG_USER_ONLY
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG)) {
+    if (cpu->cfg.debug) {
         riscv_trigger_init(env);
     }
 
@@ -935,10 +935,6 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         }
     }
 
-    if (cpu->cfg.debug) {
-        riscv_set_feature(env, RISCV_FEATURE_DEBUG);
-    }
-
 
 #ifndef CONFIG_USER_ONLY
     if (cpu->cfg.ext_sstc) {
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 00a464c9c4..46de6f2f7f 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -89,7 +89,6 @@ enum {
     RISCV_FEATURE_MMU,
     RISCV_FEATURE_PMP,
     RISCV_FEATURE_EPMP,
-    RISCV_FEATURE_DEBUG
 };
 
 /* Privileged specification version */
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index ad8d82662c..4cdd247c6c 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -105,7 +105,7 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
         flags = FIELD_DP32(flags, TB_FLAGS, MSTATUS_HS_VS,
                            get_field(env->mstatus_hs, MSTATUS_VS));
     }
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG) && !icount_enabled()) {
+    if (cpu->cfg.debug && !icount_enabled()) {
         flags = FIELD_DP32(flags, TB_FLAGS, ITRIGGER, env->itrigger_enabled);
     }
 #endif
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index e949e6248a..120a0541bb 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -437,7 +437,7 @@ static RISCVException epmp(CPURISCVState *env, int csrno)
 
 static RISCVException debug(CPURISCVState *env, int csrno)
 {
-    if (riscv_feature(env, RISCV_FEATURE_DEBUG)) {
+    if (riscv_cpu_cfg(env).debug) {
         return RISCV_EXCP_NONE;
     }
 
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index c6ce318cce..4634968898 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -226,9 +226,8 @@ static const VMStateDescription vmstate_kvmtimer = {
 static bool debug_needed(void *opaque)
 {
     RISCVCPU *cpu = opaque;
-    CPURISCVState *env = &cpu->env;
 
-    return riscv_feature(env, RISCV_FEATURE_DEBUG);
+    return cpu->cfg.debug;
 }
 
 static int debug_post_load(void *opaque, int version_id)
-- 
2.39.1

[PATCH v2 06/11] target/riscv/cpu.c: error out if EPMP is enabled without PMP

[Daniel Henrique Barboza]

Instead of silently ignoring the EPMP setting if there is no PMP
available, error out informing the user that EPMP depends on PMP
support:

$ ./qemu-system-riscv64 -cpu rv64,pmp=false,x-epmp=true
qemu-system-riscv64: Invalid configuration: EPMP requires PMP support

This will force users to pick saner options in the QEMU command line.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 272cf1a8bf..1e67e72f90 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -925,13 +925,18 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
 
     if (cpu->cfg.pmp) {
         riscv_set_feature(env, RISCV_FEATURE_PMP);
+    }
+
+    if (cpu->cfg.epmp) {
+        riscv_set_feature(env, RISCV_FEATURE_EPMP);
 
         /*
          * Enhanced PMP should only be available
          * on harts with PMP support
          */
-        if (cpu->cfg.epmp) {
-            riscv_set_feature(env, RISCV_FEATURE_EPMP);
+        if (!cpu->cfg.pmp) {
+            error_setg(errp, "Invalid configuration: EPMP requires PMP support");
+            return;
         }
     }
 
-- 
2.39.1

[PATCH v2 07/11] target/riscv: remove RISCV_FEATURE_EPMP

[Daniel Henrique Barboza]

RISCV_FEATURE_EPMP is always set to the same value as the cpu->cfg.epmp
flag. Use the flag directly.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 10 +++-------
 target/riscv/cpu.h |  1 -
 target/riscv/csr.c |  2 +-
 target/riscv/pmp.c |  4 ++--
 4 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 1e67e72f90..430b6adccb 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -927,17 +927,13 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         riscv_set_feature(env, RISCV_FEATURE_PMP);
     }
 
-    if (cpu->cfg.epmp) {
-        riscv_set_feature(env, RISCV_FEATURE_EPMP);
-
+    if (cpu->cfg.epmp && !cpu->cfg.pmp) {
         /*
          * Enhanced PMP should only be available
          * on harts with PMP support
          */
-        if (!cpu->cfg.pmp) {
-            error_setg(errp, "Invalid configuration: EPMP requires PMP support");
-            return;
-        }
+        error_setg(errp, "Invalid configuration: EPMP requires PMP support");
+        return;
     }
 
 
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 46de6f2f7f..d0de11fd41 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -88,7 +88,6 @@
 enum {
     RISCV_FEATURE_MMU,
     RISCV_FEATURE_PMP,
-    RISCV_FEATURE_EPMP,
 };
 
 /* Privileged specification version */
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 120a0541bb..223162af5e 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -428,7 +428,7 @@ static RISCVException pmp(CPURISCVState *env, int csrno)
 
 static RISCVException epmp(CPURISCVState *env, int csrno)
 {
-    if (env->priv == PRV_M && riscv_feature(env, RISCV_FEATURE_EPMP)) {
+    if (env->priv == PRV_M && riscv_cpu_cfg(env).epmp) {
         return RISCV_EXCP_NONE;
     }
 
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 4bc4113531..bb54899635 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -88,7 +88,7 @@ static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
     if (pmp_index < MAX_RISCV_PMPS) {
         bool locked = true;
 
-        if (riscv_feature(env, RISCV_FEATURE_EPMP)) {
+        if (riscv_cpu_cfg(env).epmp) {
             /* mseccfg.RLB is set */
             if (MSECCFG_RLB_ISSET(env)) {
                 locked = false;
@@ -239,7 +239,7 @@ static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
 {
     bool ret;
 
-    if (riscv_feature(env, RISCV_FEATURE_EPMP)) {
+    if (riscv_cpu_cfg(env).epmp) {
         if (MSECCFG_MMWP_ISSET(env)) {
             /*
              * The Machine Mode Whitelist Policy (mseccfg.MMWP) is set
-- 
2.39.1

[PATCH v2 08/11] target/riscv: remove RISCV_FEATURE_PMP

[Daniel Henrique Barboza]

RISCV_FEATURE_PMP is being set via riscv_set_feature() by mirroring the
cpu->cfg.pmp flag. Use the flag instead.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c        | 4 ----
 target/riscv/cpu.h        | 1 -
 target/riscv/cpu_helper.c | 2 +-
 target/riscv/csr.c        | 2 +-
 target/riscv/machine.c    | 3 +--
 target/riscv/op_helper.c  | 2 +-
 target/riscv/pmp.c        | 2 +-
 7 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 430b6adccb..a803395ed1 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -923,10 +923,6 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         riscv_set_feature(env, RISCV_FEATURE_MMU);
     }
 
-    if (cpu->cfg.pmp) {
-        riscv_set_feature(env, RISCV_FEATURE_PMP);
-    }
-
     if (cpu->cfg.epmp && !cpu->cfg.pmp) {
         /*
          * Enhanced PMP should only be available
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index d0de11fd41..62919cd5cc 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -87,7 +87,6 @@
    so a cpu features bitfield is required, likewise for optional PMP support */
 enum {
     RISCV_FEATURE_MMU,
-    RISCV_FEATURE_PMP,
 };
 
 /* Privileged specification version */
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 4cdd247c6c..15d9542691 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -706,7 +706,7 @@ static int get_physical_address_pmp(CPURISCVState *env, int *prot,
     pmp_priv_t pmp_priv;
     int pmp_index = -1;
 
-    if (!riscv_feature(env, RISCV_FEATURE_PMP)) {
+    if (!riscv_cpu_cfg(env).pmp) {
         *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
         return TRANSLATE_SUCCESS;
     }
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 223162af5e..356cf3c04f 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -419,7 +419,7 @@ static int aia_hmode32(CPURISCVState *env, int csrno)
 
 static RISCVException pmp(CPURISCVState *env, int csrno)
 {
-    if (riscv_feature(env, RISCV_FEATURE_PMP)) {
+    if (riscv_cpu_cfg(env).pmp) {
         return RISCV_EXCP_NONE;
     }
 
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index 4634968898..67e9e56853 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -27,9 +27,8 @@
 static bool pmp_needed(void *opaque)
 {
     RISCVCPU *cpu = opaque;
-    CPURISCVState *env = &cpu->env;
 
-    return riscv_feature(env, RISCV_FEATURE_PMP);
+    return cpu->cfg.pmp;
 }
 
 static int pmp_post_load(void *opaque, int version_id)
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 48f918b71b..f34701b443 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -195,7 +195,7 @@ target_ulong helper_mret(CPURISCVState *env)
     uint64_t mstatus = env->mstatus;
     target_ulong prev_priv = get_field(mstatus, MSTATUS_MPP);
 
-    if (riscv_feature(env, RISCV_FEATURE_PMP) &&
+    if (riscv_cpu_cfg(env).pmp &&
         !pmp_get_num_rules(env) && (prev_priv != PRV_M)) {
         riscv_raise_exception(env, RISCV_EXCP_INST_ACCESS_FAULT, GETPC());
     }
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index bb54899635..1e7903dffa 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -265,7 +265,7 @@ static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
         }
     }
 
-    if ((!riscv_feature(env, RISCV_FEATURE_PMP)) || (mode == PRV_M)) {
+    if (!riscv_cpu_cfg(env).pmp || (mode == PRV_M)) {
         /*
          * Privileged spec v1.10 states if HW doesn't implement any PMP entry
          * or no PMP entry matches an M-Mode access, the access succeeds.
-- 
2.39.1

[PATCH v2 09/11] hw/riscv/virt.c: do not use RISCV_FEATURE_MMU in create_fdt_socket_cpus()

[Daniel Henrique Barboza]

Read cpu_ptr->cfg.mmu directly. As a bonus, use cpu_ptr in
riscv_isa_string().

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 hw/riscv/virt.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 86c4adc0c9..49f2c157f7 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -232,20 +232,21 @@ static void create_fdt_socket_cpus(RISCVVirtState *s, int socket,
     bool is_32_bit = riscv_is_32bit(&s->soc[0]);
 
     for (cpu = s->soc[socket].num_harts - 1; cpu >= 0; cpu--) {
+        RISCVCPU *cpu_ptr = &s->soc[socket].harts[cpu];
+
         cpu_phandle = (*phandle)++;
 
         cpu_name = g_strdup_printf("/cpus/cpu@%d",
             s->soc[socket].hartid_base + cpu);
         qemu_fdt_add_subnode(ms->fdt, cpu_name);
-        if (riscv_feature(&s->soc[socket].harts[cpu].env,
-                          RISCV_FEATURE_MMU)) {
+        if (cpu_ptr->cfg.mmu) {
             qemu_fdt_setprop_string(ms->fdt, cpu_name, "mmu-type",
                                     (is_32_bit) ? "riscv,sv32" : "riscv,sv48");
         } else {
             qemu_fdt_setprop_string(ms->fdt, cpu_name, "mmu-type",
                                     "riscv,none");
         }
-        name = riscv_isa_string(&s->soc[socket].harts[cpu]);
+        name = riscv_isa_string(cpu_ptr);
         qemu_fdt_setprop_string(ms->fdt, cpu_name, "riscv,isa", name);
         g_free(name);
         qemu_fdt_setprop_string(ms->fdt, cpu_name, "compatible", "riscv");
-- 
2.39.1

[PATCH v2 10/11] target/riscv: remove RISCV_FEATURE_MMU

[Daniel Henrique Barboza]

RISCV_FEATURE_MMU is set whether cpu->cfg.mmu is set, so let's just use
the flag directly instead.

With this change the enum is also removed. It is worth noticing that
this enum, and all the RISCV_FEATURES_* that were contained in it,
predates the existence of the cpu->cfg object. Today, using cpu->cfg is
an easier way to retrieve all the features and extensions enabled in the
hart.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c        | 4 ----
 target/riscv/cpu.h        | 7 -------
 target/riscv/cpu_helper.c | 2 +-
 target/riscv/csr.c        | 4 ++--
 target/riscv/monitor.c    | 2 +-
 target/riscv/pmp.c        | 2 +-
 6 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index a803395ed1..2859ebc3e6 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -919,10 +919,6 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
         }
     }
 
-    if (cpu->cfg.mmu) {
-        riscv_set_feature(env, RISCV_FEATURE_MMU);
-    }
-
     if (cpu->cfg.epmp && !cpu->cfg.pmp) {
         /*
          * Enhanced PMP should only be available
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 62919cd5cc..83a9fa38d9 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -81,13 +81,6 @@
 #define RVH RV('H')
 #define RVJ RV('J')
 
-/* S extension denotes that Supervisor mode exists, however it is possible
-   to have a core that support S mode but does not have an MMU and there
-   is currently no bit in misa to indicate whether an MMU exists or not
-   so a cpu features bitfield is required, likewise for optional PMP support */
-enum {
-    RISCV_FEATURE_MMU,
-};
 
 /* Privileged specification version */
 enum {
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 15d9542691..e76b206191 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -796,7 +796,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
         mode = PRV_U;
     }
 
-    if (mode == PRV_M || !riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (mode == PRV_M || !riscv_cpu_cfg(env).mmu) {
         *physical = addr;
         *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
         return TRANSLATE_SUCCESS;
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 356cf3c04f..54bcdbc4dc 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -2621,7 +2621,7 @@ static RISCVException rmw_siph(CPURISCVState *env, int csrno,
 static RISCVException read_satp(CPURISCVState *env, int csrno,
                                 target_ulong *val)
 {
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env).mmu) {
         *val = 0;
         return RISCV_EXCP_NONE;
     }
@@ -2640,7 +2640,7 @@ static RISCVException write_satp(CPURISCVState *env, int csrno,
 {
     target_ulong vm, mask;
 
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env).mmu) {
         return RISCV_EXCP_NONE;
     }
 
diff --git a/target/riscv/monitor.c b/target/riscv/monitor.c
index 236f93b9f5..b7b8d0614f 100644
--- a/target/riscv/monitor.c
+++ b/target/riscv/monitor.c
@@ -218,7 +218,7 @@ void hmp_info_mem(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+    if (!riscv_cpu_cfg(env).mmu) {
         monitor_printf(mon, "S-mode MMU unavailable\n");
         return;
     }
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index 1e7903dffa..c67de36942 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -315,7 +315,7 @@ int pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
     }
 
     if (size == 0) {
-        if (riscv_feature(env, RISCV_FEATURE_MMU)) {
+        if (riscv_cpu_cfg(env).mmu) {
             /*
              * If size is unknown (0), assume that all bytes
              * from addr to the end of the page will be accessed.
-- 
2.39.1

[PATCH v2 11/11] target/riscv/cpu: remove CPUArchState::features and friends

[Daniel Henrique Barboza]

The attribute is no longer used since we can retrieve all the enabled
features in the hart by using cpu->cfg instead.

Remove env->feature, riscv_feature() and riscv_set_feature(). We also
need to bump vmstate_riscv_cpu version_id and minimal_version_id since
'features' is no longer being migrated.

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.h     | 12 ------------
 target/riscv/machine.c |  5 ++---
 2 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 83a9fa38d9..6290c6d357 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -173,8 +173,6 @@ struct CPUArchState {
     /* 128-bit helpers upper part return value */
     target_ulong retxh;
 
-    uint32_t features;
-
 #ifdef CONFIG_USER_ONLY
     uint32_t elf_flags;
 #endif
@@ -525,16 +523,6 @@ static inline int riscv_has_ext(CPURISCVState *env, target_ulong ext)
     return (env->misa_ext & ext) != 0;
 }
 
-static inline bool riscv_feature(CPURISCVState *env, int feature)
-{
-    return env->features & (1ULL << feature);
-}
-
-static inline void riscv_set_feature(CPURISCVState *env, int feature)
-{
-    env->features |= (1ULL << feature);
-}
-
 #include "cpu_user.h"
 
 extern const char * const riscv_int_regnames[];
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index 67e9e56853..9c455931d8 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -331,8 +331,8 @@ static const VMStateDescription vmstate_pmu_ctr_state = {
 
 const VMStateDescription vmstate_riscv_cpu = {
     .name = "cpu",
-    .version_id = 6,
-    .minimum_version_id = 6,
+    .version_id = 7,
+    .minimum_version_id = 7,
     .post_load = riscv_cpu_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINTTL_ARRAY(env.gpr, RISCVCPU, 32),
@@ -351,7 +351,6 @@ const VMStateDescription vmstate_riscv_cpu = {
         VMSTATE_UINT32(env.misa_ext, RISCVCPU),
         VMSTATE_UINT32(env.misa_mxl_max, RISCVCPU),
         VMSTATE_UINT32(env.misa_ext_mask, RISCVCPU),
-        VMSTATE_UINT32(env.features, RISCVCPU),
         VMSTATE_UINTTL(env.priv, RISCVCPU),
         VMSTATE_UINTTL(env.virt, RISCVCPU),
         VMSTATE_UINT64(env.resetvec, RISCVCPU),
-- 
2.39.1

Re: [PATCH v2 03/11] target/riscv: allow users to actually write the MISA CSR

[Bin Meng]

On Wed, Feb 15, 2023 at 3:26 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> At this moment, and apparently since ever, we have no way of enabling
> RISCV_FEATURE_MISA. This means that all the code from write_misa(), all
> the nuts and bolts that handles how to properly write this CSR, has
> always been a no-op as well because write_misa() will always exit
> earlier.
>
> This seems to be benign in the majority of cases. Booting an Ubuntu
> 'virt' guest and logging all the calls to 'write_misa' shows that no
> writes to MISA CSR was attempted. Writing MISA, i.e. enabling/disabling
> RISC-V extensions after the machine is powered on, seems to be a niche
> use.
>
> There is a good chance that the code in write_misa() hasn't been
> properly tested. Allowing users to write MISA can open the floodgates of
> new breeds of bugs. We could instead remove most (if not all) of
> write_misa() since it's never used. Well, as a hardware emulator,
> dealing with crashes because a register write went wrong is what we're
> here for.
>
> Create a 'misa-w' CPU property to allow users to choose whether writes
> to MISA should be allowed. The default is set to 'false' for all RISC-V
> machines to keep compatibility with what we´ve been doing so far.
>
> Read cpu->cfg.misa_w directly in write_misa(), instead of executing
> riscv_set_feature(RISCV_FEATURE_MISA) in riscv_cpu_realize(), that would
> simply reflect the cpu->cfg.misa_w bool value in 'env->features' and
> require a riscv_feature() call to read it back.

I am surprised to see we have a RISCV_FEATURE_MISA. Per spec MISA is a
WARL read-write CSR. I don't think creating a special config property
for a read-write CSR makes sense.

We should drop the feature enum and the feature check in write_misa() directly.

>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 1 +
>  target/riscv/cpu.h | 1 +
>  target/riscv/csr.c | 2 +-
>  3 files changed, 3 insertions(+), 1 deletion(-)
>

Regards,
Bin

Re: [PATCH v2 01/11] target/riscv: do not mask unsupported QEMU extensions in write_misa()

[Bin Meng]

On Wed, Feb 15, 2023 at 3:26 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The masking done using env->misa_ext_mask already filters any extension
> that QEMU doesn't support. If the hart supports the extension then QEMU
> supports it as well.
>
> If the masking done by env->misa_ext_mask is somehow letting unsupported
> QEMU extensions pass by, misa_ext_mask itself needs to be fixed instead.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/csr.c | 3 ---
>  1 file changed, 3 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 02/11] target/riscv: introduce riscv_cpu_cfg()

[Bin Meng]

On Wed, Feb 15, 2023 at 3:26 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> We're going to do changes that requires accessing the RISCVCPUConfig
> struct from the RISCVCPU, having access only to a CPURISCVState 'env'
> pointer. Add a helper to make the code easier to read.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.h | 5 +++++
>  1 file changed, 5 insertions(+)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 05/11] target/riscv: remove RISCV_FEATURE_DEBUG

[Bin Meng]

On Wed, Feb 15, 2023 at 3:25 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> RISCV_FEATURE_DEBUG will always follow the value defined by
> cpu->cfg.debug flag. Read the flag instead.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c        | 6 +-----
>  target/riscv/cpu.h        | 1 -
>  target/riscv/cpu_helper.c | 2 +-
>  target/riscv/csr.c        | 2 +-
>  target/riscv/machine.c    | 3 +--
>  5 files changed, 4 insertions(+), 10 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 06/11] target/riscv/cpu.c: error out if EPMP is enabled without PMP

[Bin Meng]

On Wed, Feb 15, 2023 at 3:24 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Instead of silently ignoring the EPMP setting if there is no PMP
> available, error out informing the user that EPMP depends on PMP
> support:
>
> $ ./qemu-system-riscv64 -cpu rv64,pmp=false,x-epmp=true
> qemu-system-riscv64: Invalid configuration: EPMP requires PMP support
>
> This will force users to pick saner options in the QEMU command line.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 07/11] target/riscv: remove RISCV_FEATURE_EPMP

[Bin Meng]

On Wed, Feb 15, 2023 at 3:25 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> RISCV_FEATURE_EPMP is always set to the same value as the cpu->cfg.epmp
> flag. Use the flag directly.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 10 +++-------
>  target/riscv/cpu.h |  1 -
>  target/riscv/csr.c |  2 +-
>  target/riscv/pmp.c |  4 ++--
>  4 files changed, 6 insertions(+), 11 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 08/11] target/riscv: remove RISCV_FEATURE_PMP

[Bin Meng]

On Wed, Feb 15, 2023 at 3:25 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> RISCV_FEATURE_PMP is being set via riscv_set_feature() by mirroring the
> cpu->cfg.pmp flag. Use the flag instead.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c        | 4 ----
>  target/riscv/cpu.h        | 1 -
>  target/riscv/cpu_helper.c | 2 +-
>  target/riscv/csr.c        | 2 +-
>  target/riscv/machine.c    | 3 +--
>  target/riscv/op_helper.c  | 2 +-
>  target/riscv/pmp.c        | 2 +-
>  7 files changed, 5 insertions(+), 11 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 09/11] hw/riscv/virt.c: do not use RISCV_FEATURE_MMU in create_fdt_socket_cpus()

[Bin Meng]

On Wed, Feb 15, 2023 at 3:25 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Read cpu_ptr->cfg.mmu directly. As a bonus, use cpu_ptr in
> riscv_isa_string().
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  hw/riscv/virt.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 10/11] target/riscv: remove RISCV_FEATURE_MMU

[Bin Meng]

On Wed, Feb 15, 2023 at 3:27 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> RISCV_FEATURE_MMU is set whether cpu->cfg.mmu is set, so let's just use
> the flag directly instead.
>
> With this change the enum is also removed. It is worth noticing that
> this enum, and all the RISCV_FEATURES_* that were contained in it,
> predates the existence of the cpu->cfg object. Today, using cpu->cfg is
> an easier way to retrieve all the features and extensions enabled in the
> hart.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c        | 4 ----
>  target/riscv/cpu.h        | 7 -------
>  target/riscv/cpu_helper.c | 2 +-
>  target/riscv/csr.c        | 4 ++--
>  target/riscv/monitor.c    | 2 +-
>  target/riscv/pmp.c        | 2 +-
>  6 files changed, 5 insertions(+), 16 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 11/11] target/riscv/cpu: remove CPUArchState::features and friends

[Bin Meng]

On Wed, Feb 15, 2023 at 3:26 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The attribute is no longer used since we can retrieve all the enabled
> features in the hart by using cpu->cfg instead.
>
> Remove env->feature, riscv_feature() and riscv_set_feature(). We also
> need to bump vmstate_riscv_cpu version_id and minimal_version_id since
> 'features' is no longer being migrated.
>
> Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.h     | 12 ------------
>  target/riscv/machine.c |  5 ++---
>  2 files changed, 2 insertions(+), 15 deletions(-)
>

Reviewed-by: Bin Meng <bmeng@tinylab.org>

Re: [PATCH v2 00/11] enable write_misa() and RISCV_FEATURE_* cleanups

[Andrew Jones]

On Tue, Feb 14, 2023 at 04:23:45PM -0300, Daniel Henrique Barboza wrote:
> Hi,
> 
> This new version contains suggestions made by Weiwei Li in v1. Most
> notable change is patch 4 from v1, moving up to patch 2 now,  to allow
> the riscv_cpu_cfg() helper to be used in the MISA CSR patch.
> 
> 
> Changes in v2:
> - former patch 4 moved to patch 2
> - patch 3 (former 2):
>   - use riscv_cpu_cfg()
> - patch 9:
>   - remove the uneeded RISCVCPUConfig and access mmu via
>     cpu_cfg->cfg.mmu
> - v1 link: https://lists.gnu.org/archive/html/qemu-devel/2023-02/msg02780.html
> 
> Daniel Henrique Barboza (11):
>   target/riscv: do not mask unsupported QEMU extensions in write_misa()
>   target/riscv: introduce riscv_cpu_cfg()
>   target/riscv: allow users to actually write the MISA CSR
>   target/riscv: remove RISCV_FEATURE_MISA
>   target/riscv: remove RISCV_FEATURE_DEBUG
>   target/riscv/cpu.c: error out if EPMP is enabled without PMP
>   target/riscv: remove RISCV_FEATURE_EPMP
>   target/riscv: remove RISCV_FEATURE_PMP
>   hw/riscv/virt.c: do not use RISCV_FEATURE_MMU in
>     create_fdt_socket_cpus()
>   target/riscv: remove RISCV_FEATURE_MMU
>   target/riscv/cpu: remove CPUArchState::features and friends
> 
>  hw/riscv/virt.c           |  7 ++++---
>  target/riscv/cpu.c        | 20 +++++---------------
>  target/riscv/cpu.h        | 29 ++++++-----------------------
>  target/riscv/cpu_helper.c |  6 +++---
>  target/riscv/csr.c        | 15 ++++++---------
>  target/riscv/machine.c    | 11 ++++-------
>  target/riscv/monitor.c    |  2 +-
>  target/riscv/op_helper.c  |  2 +-
>  target/riscv/pmp.c        |  8 ++++----
>  9 files changed, 34 insertions(+), 66 deletions(-)
> 
> -- 
> 2.39.1
> 
>

For the series

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>