Re: [PATCH for-8.1 v4 24/25] target/riscv: update cpu->cfg misa bits in commit_cpu_cfg()

[liweiwei]

On 2023/3/23 06:20, Daniel Henrique Barboza wrote:
write_misa() is able to use the same validation workflow
riscv_cpu_realize() uses. But it's still not capable of updating
cpu->cfg misa props yet.
We have no way of blocking future (and current) code from checking
env->misa_ext (via riscv_has_ext()) or reading cpu->cfg directly, so our
best alternative is to keep everything in sync.

riscv_cpu_commit_cpu_cfg() now receives an extra 'misa_ext' parameter.
If this val is different from the existing env->misa_ext, update
env->misa and cpu->cfg with the new value. riscv_cpu_realize() will
ignore this code since env->misa_ext isn't touched during validation,
but write_misa() will use it to keep cpu->cfg in sync with the new
env->misa_ext value.

Signed-off-by: Daniel Henrique Barboza<dbarb...@ventanamicro.com>
---
  target/riscv/cpu.c | 16 ++++++++++++++--
  target/riscv/cpu.h |  2 +-
  target/riscv/csr.c |  3 +--
  3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 41b17ba0c3..88806d1050 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1204,8 +1204,20 @@ void riscv_cpu_validate_extensions(RISCVCPU *cpu, 
uint32_t misa_ext,
      }
  }
  
-void riscv_cpu_commit_cpu_cfg(RISCVCPU *cpu)
+void riscv_cpu_commit_cpu_cfg(RISCVCPU *cpu, uint32_t misa_ext)
  {
+    CPURISCVState *env = &cpu->env;
+
+    /*
+     * write_misa() needs to update cpu->cfg with the new
+     * MISA bits. This is a no-op for the riscv_cpu_realize()
+     * path.
+     */
+    if (env->misa_ext != misa_ext) {
+        env->misa_ext = misa_ext;
+        riscv_set_cpucfg_with_misa(&cpu->cfg, misa_ext);
+    }
+
      if (cpu->cfg.ext_zk) {
          cpu->cfg.ext_zkn = true;
          cpu->cfg.ext_zkr = true;

These zk* related assignment and riscv_cpu_disable_priv_spec_isa_exts() 
can be moved to other places.

They needn't be done for write_misa.

Regards,

Weiwei Li

@@ -1374,7 +1386,7 @@ static void riscv_cpu_realize(DeviceState *dev, Error 
**errp)
          return;
      }
  
-    riscv_cpu_commit_cpu_cfg(cpu);
+    riscv_cpu_commit_cpu_cfg(cpu, env->misa_ext);
  
  #ifndef CONFIG_USER_ONLY
      if (cpu->cfg.ext_sstc) {
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index ca2ba6a647..befc3b8fff 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -597,7 +597,7 @@ void riscv_cpu_validate_misa_ext(CPURISCVState *env, 
uint32_t misa_ext,
                                   Error **errp);
  void riscv_cpu_validate_extensions(RISCVCPU *cpu, uint32_t misa_ext,
                                     Error **errp);
-void riscv_cpu_commit_cpu_cfg(RISCVCPU *cpu);
+void riscv_cpu_commit_cpu_cfg(RISCVCPU *cpu, uint32_t misa_ext);
  
  #define cpu_list riscv_cpu_list
  #define cpu_mmu_index riscv_cpu_mmu_index
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 8d5e8f9ad1..839862f1a8 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -1396,7 +1396,7 @@ static RISCVException write_misa(CPURISCVState *env, int 
csrno,
          return RISCV_EXCP_NONE;
      }
  
-    riscv_cpu_commit_cpu_cfg(cpu);
+    riscv_cpu_commit_cpu_cfg(cpu, val);
  
      if (!(val & RVF)) {
          env->mstatus &= ~MSTATUS_FS;
@@ -1404,7 +1404,6 @@ static RISCVException write_misa(CPURISCVState *env, int 
csrno,
  
      /* flush translation cache */
      tb_flush(env_cpu(env));
-    env->misa_ext = val;
      env->xl = riscv_cpu_mxl(env);
      return RISCV_EXCP_NONE;
  }