Re: [Qemu-devel] [RFC PATCH V4 0/6] icount: Implement delay algorithm between guest and host clocks

[Sebastian Tanase <sebastian.tanase@openwide.fr>]

----- Mail original -----
> De: "Paolo Bonzini" <pbonzini@redhat.com>
> À: "Sebastian Tanase" <sebastian.tanase@openwide.fr>, qemu-devel@nongnu.org
> Cc: aliguori@amazon.com, afaerber@suse.de, rth@twiddle.net, "peter maydell" <peter.maydell@linaro.org>,
> michael@walle.cc, alex@alex.org.uk, stefanha@redhat.com, lcapitulino@redhat.com, crobinso@redhat.com,
> armbru@redhat.com, wenchaoqemu@gmail.com, quintela@redhat.com, kwolf@redhat.com, mst@redhat.com, "camille begue"
> <camille.begue@openwide.fr>
> Envoyé: Mercredi 16 Juillet 2014 15:20:00
> Objet: Re: [RFC PATCH V4 0/6] icount: Implement delay algorithm between guest and host clocks
> 
> Il 16/07/2014 14:18, Sebastian Tanase ha scritto:
> > v3 -> v4
> >
> > * Add better error handling for 'strtol' in patch 2
> > * Add 'Sleep' instead of 'nanosleep' for Windows hosts in patch 4
> > * Remove function pointers from patches 4 and 5
> 
> Hi Sebastian, I think we're getting really close.
> 
> I asked a question about clocks_offset; I think it's not necessary to
> compute it in cpu-exec.c because the same information is available
> elsewhere.  It is also probably not necessary to make it public.  Can
> you please check this?  Once this is sorted out, the patch should be
> ready for inclusion in 2.2.
> 
> Thanks for your effort!
> 
> Paolo
> 

Hello,

Supposing the patch that changes vm_clock_warp_start from 0 to -1 is accepted,
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.


Best regards,

Sebastian