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From: Richard Henderson <rth@twiddle.net>
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Date: Thu, 7 Dec 2017 16:00:50 -0800
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Subject: Re: [Qemu-devel] [PATCH v2 for-2.12 3/5] s390x/tcg: implement SET
 CLOCK PROGRAMMABLE FIELD
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To: David Hildenbrand <david@redhat.com>, qemu-s390x@nongnu.org, qemu-devel@nongnu.org
Cc: Christian Borntraeger <borntraeger@de.ibm.com>, Cornelia Huck <cohuck@redhat.com>, Alexander Graf <agraf@suse.de>

On 12/07/2017 07:31 AM, David Hildenbrand wrote:
> +DEF_HELPER_FLAGS_1(sckpf, TCG_CALL_NO_RWG, void, env)
...
> +/* Set Tod Programmable Field */
> +void HELPER(sckpf)(CPUS390XState *env)
> +{
> +    uint32_t val = env->regs[0];
> +
> +    if (val & 0xffff0000) {
> +        s390_program_interrupt(env, PGM_SPECIFICATION, 2, GETPC());
> +    }
> +    env->todpr = val;
> +}

You do read a tcg global -- regs[0].  Either pass in r0 as a parameter or use
TCG_CALL_NO_WG.


r~