[v2] target/riscv: Fix a uninitialized variable warning

[PATCH v2] target/riscv: Fix a uninitialized variable warning

Posted by Akihiko Odaki 3 weeks, 3 days ago

riscv_cpu_validate_v() left its variable, min_vlen, uninitialized if
no vector extension is available, causing a compiler warning.

Re-define riscv_cpu_validate_v() as no-op when no vector extension is
available to prevent the scenario that will read the unintialized
variable by construction. It also simplifies its caller as a bonus.

Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
---
Changes in v2:
- De-duplicated zve32f checks as suggested by Daniel Henrique Barboza.
- Link to v1: https://lore.kernel.org/qemu-devel/20251019-vlen-v1-1-f7352a402f06@rsg.ci.i.u-tokyo.ac.jp
---
 target/riscv/tcg/tcg-cpu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 1150bd14697c..d3968251fad5 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -426,6 +426,8 @@ static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
         min_vlen = 64;
     } else if (cfg->ext_zve32x) {
         min_vlen = 32;
+    } else {
+        return;
     }
 
     if (vlen > RV_VLEN_MAX || vlen < min_vlen) {
@@ -676,12 +678,10 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
         return;
     }
 
-    if (cpu->cfg.ext_zve32x) {
-        riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
-        if (local_err != NULL) {
-            error_propagate(errp, local_err);
-            return;
-        }
+    riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
+    if (local_err != NULL) {
+        error_propagate(errp, local_err);
+        return;
     }
 
     /* The Zve64d extension depends on the Zve64f extension */

---
base-commit: c85ba2d7a4056595166689890285105579db446a
change-id: 20251019-vlen-30a57c03bd93

Best regards,
--  
Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

Re: [PATCH v2] target/riscv: Fix a uninitialized variable warning

Posted by Alistair Francis 3 weeks, 1 day ago

On Tue, Oct 21, 2025 at 3:09 PM Akihiko Odaki
<odaki@rsg.ci.i.u-tokyo.ac.jp> wrote:
>
> riscv_cpu_validate_v() left its variable, min_vlen, uninitialized if
> no vector extension is available, causing a compiler warning.
>
> Re-define riscv_cpu_validate_v() as no-op when no vector extension is
> available to prevent the scenario that will read the unintialized
> variable by construction. It also simplifies its caller as a bonus.
>
> Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
> Changes in v2:
> - De-duplicated zve32f checks as suggested by Daniel Henrique Barboza.
> - Link to v1: https://lore.kernel.org/qemu-devel/20251019-vlen-v1-1-f7352a402f06@rsg.ci.i.u-tokyo.ac.jp
> ---
>  target/riscv/tcg/tcg-cpu.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 1150bd14697c..d3968251fad5 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -426,6 +426,8 @@ static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
>          min_vlen = 64;
>      } else if (cfg->ext_zve32x) {
>          min_vlen = 32;
> +    } else {
> +        return;
>      }
>
>      if (vlen > RV_VLEN_MAX || vlen < min_vlen) {
> @@ -676,12 +678,10 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
>          return;
>      }
>
> -    if (cpu->cfg.ext_zve32x) {
> -        riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
> -        if (local_err != NULL) {
> -            error_propagate(errp, local_err);
> -            return;
> -        }
> +    riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
> +    if (local_err != NULL) {
> +        error_propagate(errp, local_err);
> +        return;
>      }
>
>      /* The Zve64d extension depends on the Zve64f extension */
>
> ---
> base-commit: c85ba2d7a4056595166689890285105579db446a
> change-id: 20251019-vlen-30a57c03bd93
>
> Best regards,
> --
> Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
>
>

Re: [PATCH v2] target/riscv: Fix a uninitialized variable warning

Posted by Daniel Henrique Barboza 3 weeks, 3 days ago


On 10/21/25 2:07 AM, Akihiko Odaki wrote:
> riscv_cpu_validate_v() left its variable, min_vlen, uninitialized if
> no vector extension is available, causing a compiler warning.
> 
> Re-define riscv_cpu_validate_v() as no-op when no vector extension is
> available to prevent the scenario that will read the unintialized
> variable by construction. It also simplifies its caller as a bonus.
> 
> Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> ---

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>


> Changes in v2:
> - De-duplicated zve32f checks as suggested by Daniel Henrique Barboza.
> - Link to v1: https://lore.kernel.org/qemu-devel/20251019-vlen-v1-1-f7352a402f06@rsg.ci.i.u-tokyo.ac.jp
> ---
>   target/riscv/tcg/tcg-cpu.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 1150bd14697c..d3968251fad5 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -426,6 +426,8 @@ static void riscv_cpu_validate_v(CPURISCVState *env, RISCVCPUConfig *cfg,
>           min_vlen = 64;
>       } else if (cfg->ext_zve32x) {
>           min_vlen = 32;
> +    } else {
> +        return;
>       }
>   
>       if (vlen > RV_VLEN_MAX || vlen < min_vlen) {
> @@ -676,12 +678,10 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
>           return;
>       }
>   
> -    if (cpu->cfg.ext_zve32x) {
> -        riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
> -        if (local_err != NULL) {
> -            error_propagate(errp, local_err);
> -            return;
> -        }
> +    riscv_cpu_validate_v(env, &cpu->cfg, &local_err);
> +    if (local_err != NULL) {
> +        error_propagate(errp, local_err);
> +        return;
>       }
>   
>       /* The Zve64d extension depends on the Zve64f extension */
> 
> ---
> base-commit: c85ba2d7a4056595166689890285105579db446a
> change-id: 20251019-vlen-30a57c03bd93
> 
> Best regards,
> --
> Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
>