Re: [PATCH v3 02/14] target/s390x: Fix CLM with M3=0

[Richard Henderson <richard.henderson@linaro.org>]

On 7/19/23 23:11, Ilya Leoshkevich wrote:
> When the mask is zero, access exceptions should still be recognized for
> 1 byte at the second-operand address. CC should be set to 0.
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Cc: qemu-stable@nongnu.org
> Fixes: defb0e3157af ("s390x: Implement opcode helpers")
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   target/s390x/tcg/mem_helper.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
> index f417fb1183c..d6dc8b32620 100644
> --- a/target/s390x/tcg/mem_helper.c
> +++ b/target/s390x/tcg/mem_helper.c
> @@ -667,6 +667,11 @@ uint32_t HELPER(clm)(CPUS390XState *env, uint32_t r1, uint32_t mask,
>       HELPER_LOG("%s: r1 0x%x mask 0x%x addr 0x%" PRIx64 "\n", __func__, r1,
>                  mask, addr);
>   
> +    if (!mask) {
> +        /* Recognize access exceptions for the first byte */
> +        cpu_ldub_data_ra(env, addr, ra);
> +    }

Since s390x does not implement .do_transaction_failed, I guess this is ok.
But probe_read might be clearer.

Anyway,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

> +
>       while (mask) {
>           if (mask & 8) {
>               uint8_t d = cpu_ldub_data_ra(env, addr, ra);