Re: [RFC PATCH v3 04/21] target/arm: Implement ALLINT MSR (immediate)

[Richard Henderson]

On 2/23/24 00:32, Jinjie Ruan via wrote:
> Add ALLINT MSR (immediate) to decodetree. And the EL0 check is necessary
> to ALLINT. Avoid the unconditional write to pc and use raise_exception_ra
> to unwind.
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
> v3:
> - Remove EL0 check in allint_check().
> - Add TALLINT check for EL1 in allint_check().
> - Remove unnecessarily arm_rebuild_hflags() in msr_i_allint helper.
> ---
>   target/arm/tcg/a64.decode      |  1 +
>   target/arm/tcg/helper-a64.c    | 24 ++++++++++++++++++++++++
>   target/arm/tcg/helper-a64.h    |  1 +
>   target/arm/tcg/translate-a64.c | 10 ++++++++++
>   4 files changed, 36 insertions(+)
>
> diff --git a/target/arm/tcg/a64.decode b/target/arm/tcg/a64.decode
> index 8a20dce3c8..3588080024 100644
> --- a/target/arm/tcg/a64.decode
> +++ b/target/arm/tcg/a64.decode
> @@ -207,6 +207,7 @@ MSR_i_DIT       1101 0101 0000 0 011 0100 .... 010 11111 
> @msr_i
>   MSR_i_TCO       1101 0101 0000 0 011 0100 .... 100 11111 @msr_i
>   MSR_i_DAIFSET   1101 0101 0000 0 011 0100 .... 110 11111 @msr_i
>   MSR_i_DAIFCLEAR 1101 0101 0000 0 011 0100 .... 111 11111 @msr_i
> +MSR_i_ALLINT    1101 0101 0000 0 001 0100 .... 000 11111 @msr_i

Decode is incorrect either here, or in trans_MSR_i_ALLINT, because CRm != 
'000x' is UNDEFINED.

MSR_i_ALLINT    1101 0101 0000 0 001 0100 000 imm:1 000 11111

is perhaps the clearest implementation.

> +static void allint_check(CPUARMState *env, uint32_t op,
> +                       uint32_t imm, uintptr_t ra)
> +{
> +    /* ALLINT update to PSTATE. */
> +    if (arm_current_el(env) == 1 && arm_is_el2_enabled(env) &&
> +        (arm_hcrx_el2_eff(env) & HCRX_TALLINT)) {
> +        raise_exception_ra(env, EXCP_UDEF,
> +                           syn_aa64_sysregtrap(0, extract32(op, 0, 3),
> +                                               extract32(op, 3, 3), 4,
> +                                               imm, 0x1f, 0),
> +                           exception_target_el(env), ra);
> +    }
> +}
> +
> +void HELPER(msr_i_allint)(CPUARMState *env, uint32_t imm)
> +{
> +    allint_check(env, 0x8, imm, GETPC());

As previously noted, the check for MSR_i only applies to imm==1, not 0.

As previously noted, with ALLINT in env->pstate, you can implement this completely inline 
for EL[23], or EL1 with imm==0.

No point in passing in "op" and extracting, because you know exactly what the value should 
be for all MSR ALLINT.


r~