[PATCH] target/riscv: don't verify ISA compatibility for zicntr and zihpm

[PATCH] target/riscv: don't verify ISA compatibility for zicntr and zihpm

[Clément Chigot]

The extensions zicntr and zihpm were officially added in the privilege
instruction set specification 1.12. However, QEMU has been implemented
them long before it and thus they are forced to be on during the cpu
initialization to ensure compatibility (see riscv_cpu_init).
riscv_cpu_disable_priv_spec_isa_exts was not updated when the above
behavior was introduced, resulting in these extensions to be disabled
after all.

Signed-off-by: Clément Chigot <chigot@adacore.com>
---
 target/riscv/tcg/tcg-cpu.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 08adad304d..8a35683a34 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -250,6 +250,15 @@ static void riscv_cpu_disable_priv_spec_isa_exts(RISCVCPU *cpu)
     for (edata = isa_edata_arr; edata && edata->name; edata++) {
         if (isa_ext_is_enabled(cpu, edata->ext_enable_offset) &&
             (env->priv_ver < edata->min_version)) {
+            /*
+             * These two extensions are always enabled as they were supported
+             * by QEMU before they were added as extensions in the ISA.
+             */
+            if (!strcmp(edata->name, "zicntr") ||
+                !strcmp(edata->name, "zihpm")) {
+                continue;
+            }
+
             isa_ext_update_enabled(cpu, edata->ext_enable_offset, false);
 #ifndef CONFIG_USER_ONLY
             warn_report("disabling %s extension for hart 0x" TARGET_FMT_lx
-- 
2.25.1

Re: [PATCH] target/riscv: don't verify ISA compatibility for zicntr and zihpm

[Daniel Henrique Barboza]

(adding maintainers in the CC)



On 11/14/23 06:44, Clément Chigot wrote:
> The extensions zicntr and zihpm were officially added in the privilege
> instruction set specification 1.12. However, QEMU has been implemented
> them long before it and thus they are forced to be on during the cpu
> initialization to ensure compatibility (see riscv_cpu_init).
> riscv_cpu_disable_priv_spec_isa_exts was not updated when the above
> behavior was introduced, resulting in these extensions to be disabled
> after all.
> 

Please add the following tags:

Fixes: c004099330 ("target/riscv: add zicntr extension flag for TCG")
Fixes: 0824121660 ("target/riscv: add zihpm extension flag for TCG")

> Signed-off-by: Clément Chigot <chigot@adacore.com>
> ---

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


>   target/riscv/tcg/tcg-cpu.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
> index 08adad304d..8a35683a34 100644
> --- a/target/riscv/tcg/tcg-cpu.c
> +++ b/target/riscv/tcg/tcg-cpu.c
> @@ -250,6 +250,15 @@ static void riscv_cpu_disable_priv_spec_isa_exts(RISCVCPU *cpu)
>       for (edata = isa_edata_arr; edata && edata->name; edata++) {
>           if (isa_ext_is_enabled(cpu, edata->ext_enable_offset) &&
>               (env->priv_ver < edata->min_version)) {
> +            /*
> +             * These two extensions are always enabled as they were supported
> +             * by QEMU before they were added as extensions in the ISA.
> +             */
> +            if (!strcmp(edata->name, "zicntr") ||
> +                !strcmp(edata->name, "zihpm")) {
> +                continue;
> +            }
> +
>               isa_ext_update_enabled(cpu, edata->ext_enable_offset, false);
>   #ifndef CONFIG_USER_ONLY
>               warn_report("disabling %s extension for hart 0x" TARGET_FMT_lx