Re: [Xen-devel] [PATCH ARM v6 11/14] mini-os: arm: time

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-07-21 at 18:45 +0100, Julien Grall wrote:
> Hi Thomas,
> 
> On 07/16/2014 12:07 PM, Thomas Leonard wrote:
> > +/* These are peridically updated in shared_info, and then copied here. */
> > +struct shadow_time_info {
> > +    uint64_t tsc_timestamp;     /* TSC at last update of time vals.  */
> > +    uint64_t system_timestamp;  /* Time, in nanosecs, since boot.    */
> > +    uint32_t tsc_to_nsec_mul;
> > +    uint32_t tsc_to_usec_mul;
> > +    int tsc_shift;
> > +    uint32_t version;
> > +};
> > +static struct timespec shadow_ts;
> > +static uint32_t shadow_ts_version;
> > +
> > +static struct shadow_time_info shadow;
> > +
> > +static void get_time_values_from_xen(void)
> > +{
> > +    struct vcpu_time_info    *src = 
> > &HYPERVISOR_shared_info->vcpu_info[0].time;
> > +
> > +     do {
> > +        shadow.version = src->version;
> > +        rmb();
> > +        shadow.tsc_timestamp     = src->tsc_timestamp;
> > +        shadow.system_timestamp  = src->system_time;
> > +        shadow.tsc_to_nsec_mul   = src->tsc_to_system_mul;
> > +        shadow.tsc_shift         = src->tsc_shift;
> > +        rmb();
> > +    }
> > +    while ((src->version & 1) | (shadow.version ^ src->version));
> > +
> > +    shadow.tsc_to_usec_mul = shadow.tsc_to_nsec_mul / 1000;
> > +}
> 
> It looks the code above is the same as x86. Did you think about sharing
> the code which used Xen time?
> 
> Looking closer to this patch, nothing is using the field of this shared
> structure, which is CPU time consuming and adding line for no
> improvement. So I think you can drop all the code related the PV timer
> for now.

Does Xen even populate this struct on ARM? I'm not sure...

Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel