On Wed, 30 Sept 2026 at 10:46, Gilles Grimaud
<[email protected]> wrote:
>
> The Armv6-M Unprivileged/Privileged Extension is optional. While the
> Cortex-M0 does not implement it, the Cortex-M0+ may - and the RP2040
> Cortex-M0+ configuration in particular provides this extension.
>
> Add the cortex-m0plus CPU type, reusing the existing Cortex-M0
> initialization logic. Enable ARM_FEATURE_M_UNPRIV, introduced by commit
> 285e929908 ("target/arm: model Cortex-M0+ privilege extension"), and set
> the Cortex-M0+ MIDR used by the RP2040.
>
> Signed-off-by: Gilles Grimaud <[email protected]>
> ---
> The Cortex-M0+ CPU type was previously included in:
>
> [RFC PATCH v1 2/6] target/arm: model Cortex-M0+ privilege extension
>
> https://lore.kernel.org/qemu-devel/[email protected]/
>
> It is now submitted separately following review feedback.
>
> target/arm/tcg/cpu-v7m.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/target/arm/tcg/cpu-v7m.c b/target/arm/tcg/cpu-v7m.c
> index 48b31d5eac..ac99c93ec3 100644
> --- a/target/arm/tcg/cpu-v7m.c
> +++ b/target/arm/tcg/cpu-v7m.c
> @@ -76,6 +76,15 @@ static void cortex_m0_initfn(Object *obj)
> SET_IDREG(isar, ID_ISAR6, 0x00000000);
> }
>
> +static void cortex_m0plus_initfn(Object *obj)
> +{
> + ARMCPU *cpu = ARM_CPU(obj);
> +
> + cortex_m0_initfn(obj);
Better not to call the m0's initfn; instead set all the
features etc the M0+ needs here. (The two CPUs are named
very similarly but that doesn't mean much beyond marketing;
for QEMU's purposes they're just different CPUs.)
> + set_feature(&cpu->env, ARM_FEATURE_M_UNPRIV);
> + cpu->midr = 0x410cc601;
> +}
> +
> static void cortex_m3_initfn(Object *obj)
> {
> ARMCPU *cpu = ARM_CPU(obj);
> @@ -325,6 +334,8 @@ static void arm_v7m_class_init(ObjectClass *oc, const
> void *data)
> static const ARMCPUInfo arm_v7m_cpus[] = {
> { .name = "cortex-m0", .initfn = cortex_m0_initfn,
> .class_init = arm_v7m_class_init },
> + { .name = "cortex-m0plus", .initfn = cortex_m0plus_initfn,
> + .class_init = arm_v7m_class_init },
> { .name = "cortex-m3", .initfn = cortex_m3_initfn,
> .class_init = arm_v7m_class_init },
> { .name = "cortex-m4", .initfn = cortex_m4_initfn,
We generally prefer to add CPUs together with the board model
that uses them, so you can include this patch in your RP2040 series.
thanks
-- PMM
