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Re: [Qemu-devel] [RFC PATCH V4 0/6] icount: Implement delay algorithm be
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC PATCH V4 0/6] icount: Implement delay algorithm between guest and host clocks |
Date: |
Tue, 22 Jul 2014 16:59:18 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
Il 22/07/2014 16:02, Sebastian Tanase ha scritto:
> Yes, QEMU_CLOCK_VIRTUAL counts up from qemu_clock_get_ns(QEMU_CLOCK_REALTIME)
> on ARM (I have only tested with the versatilepb and vexpress boards).
That's a bug to fix indeed, then---it should count up from 0 without
icount, and icount shouldn't affect this. Thanks for investigating it.
> Supposing the patch that changes vm_clock_warp_start from 0 to -1 is accepted,
... which shouldn't be a problem,... :)
> I could use the information in timers_state.cpu_clock_offset instead of
> recalculating
> the offset. Besides, given that I only need this particular field from the
> whole
> structure, I think I don't have to make timers_state public; I could add a
> function
> in cpus.c, for example:
>
> int64_t cpu_get_clock_offset(void)
> {
> int64_t ti;
> unsigned start;
>
> do {
> start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
> ti = -timers_state.cpu_clock_offset;
> } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
>
> return ti;
> }
>
> that will return the cpu_clock_offset field.
Indeed what I was proposing is a bit more sloppy. If you do that, you
have to make the function a bit more general:
ti = timers_state.cpu_clock_offset;
if (!timers_state.cpu_ticks_enabled) {
ti -= get_clock();
}
...
return -ti;
even though in cpus.c you'll only be using it when cpu_ticks_enabled is
true. See cpu_enable_ticks() and cpu_disable_ticks().
Paolo
- [Qemu-devel] [RFC PATCH V4 4/6] cpu_exec: Add sleeping algorithm, (continued)
[Qemu-devel] [RFC PATCH V4 5/6] cpu_exec: Print to console if the guest is late, Sebastian Tanase, 2014/07/16
[Qemu-devel] [RFC PATCH V4 2/6] icount: Add align option to icount, Sebastian Tanase, 2014/07/16
Re: [Qemu-devel] [RFC PATCH V4 0/6] icount: Implement delay algorithm between guest and host clocks, Paolo Bonzini, 2014/07/16
Re: [Qemu-devel] [RFC PATCH V4 0/6] icount: Implement delay algorithm between guest and host clocks, Luiz Capitulino, 2014/07/16