Re: [PATCH v4 1/4] target/s390x: Fix missing interrupts for small CKC values

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Thu, 2025-11-27 at 17:43 +0100, Thomas Huth wrote:
> On 16/10/2025 19.58, Ilya Leoshkevich wrote:
> > Suppose TOD clock value is 0x1111111111111111 and clock-comparator
> > value is 0, in which case clock-comparator interruption should
> > occur
> > immediately.
> > 
> > With the current code, tod2time(env->ckc - td->base.low) ends up
> > being
> > a very large number, so this interruption never happens.
> > 
> > Fix by firing the timer immediately if env->ckc < td->base.low.
> > 
> > Cc: qemu-stable@nongnu.org
> > Reviewed-by: Thomas Huth <thuth@redhat.com>
> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> > ---
> 
>   Hi Ilya,
> 
> this patch unfortunately broke reverse debugging on the s390x target.
> Something like this used to work before:
> 
>   qemu-img create -f qcow2 /tmp/disk.qcow2 2G
>   ./qemu-system-s390x -nographic \
>     -icount shift=6,rr=record,rrfile=replay.bin,rrsnapshot=init \
>     -net none -drive file=/tmp/disk.qcow2,if=none
>   ./qemu-system-s390x -nographic \
>     -icount shift=6,rr=replay,rrfile=replay.bin,rrsnapshot=init \
>     -net none -drive file=/tmp/disk.qcow2,if=none
> 
> With this commit and later, the replay hangs somewhere in an endless
> loop.
> Do you have any ideas what could go wrong here?
> 
>   Thanks,
>    Thomas

[...]

Hi Thomas,

Thanks for letting me know, I will look at this ASAP.

Best regards,
Ilya