Re: [Qemu-devel] [Qemu-ppc] Migrating decrementer

[Mark Cave-Ayland]

On 25/02/16 05:00, Mark Cave-Ayland wrote:

> On 25/02/16 04:33, Mark Cave-Ayland wrote:
> 
>> cpu_start/resume():
>>     cpu->tb_env->tb_offset =
>>         qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) * tb_env->tb_freq +
>>             cpu->tb_env->tb_offset -
>>         qemu_clock_get_ns(QEMU_CLOCK_HOST)
> 
> Actually just realised this is slightly wrong and in fact should be:
> 
> cpu_start/resume():
>     cpu->tb_env->tb_offset =
>         muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
>                  cpu->tb_env->tb_freq, NANOSECONDS_PER_SECOND) +
>             cpu->tb_env->tb_offset -
>         qemu_clock_get_ns(QEMU_CLOCK_HOST)

Sign. And let me try that again, this time after caffeine:

cpu_start/resume():
    cpu->tb_env->tb_offset =
        muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
                 cpu->tb_env->tb_freq, NANOSECONDS_PER_SECOND) +
            cpu->tb_env->tb_offset -
        cpu_get_host_ticks();

This should translate to: at CPU start, calculate the difference between
the current guest virtual timebase and the host timebase, storing the
difference in cpu->tb_env->tb_offset.


ATB,

Mark.