Re: [PATCH RFC v3 1/3] time: add "NOW() good" indicator

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 5/22/26 9:56 AM, Jan Beulich wrote:
> On 22.05.2026 09:46, Oleksii Kurochko wrote:
> > On 5/20/26 4:45 PM, Jan Beulich wrote:
> > > printk_start_of_line() checks for a value of 0 right now. In order to be
> > > able to have NOW() return at least monotonically increasing values, that
> > > needs replacing by an explicit indicator.
> > >
> > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > > ---
> > > Arm and RISC-V may want to consider whether their initial get_cycles()
> > > can't be moved yet earlier, such that the indicator also can be set
> > > yet earlier.
> > > ---
> > At least, for RISC-V ...
> >
> > > v3: New.
> > >
> > > --- a/xen/arch/arm/time.c
> > > +++ b/xen/arch/arm/time.c
> > > @@ -145,6 +145,7 @@ void __init preinit_xen_time(void)
> > >            panic("Timer: Cannot initialize platform timer\n");
> > >    
> > >        boot_count = get_cycles();
> > > +    NOW_good = true;
> > >    }
> > >    
> > >    static void __init init_dt_xen_time(void)
> > > --- a/xen/arch/riscv/time.c
> > > +++ b/xen/arch/riscv/time.c
> > > @@ -87,6 +87,7 @@ void __init preinit_xen_time(void)
> > >            panic("%s: ACPI isn't supported\n", __func__);
> > >    
> > >        boot_clock_cycles = get_cycles();
> > > +    NOW_good = true;
> > ...  preinit_xen_time() call could be moved a little bit above just
> > after riscv_fill_hwcap() as it is using riscv_isa_extension_available()
> > inside.
> >
> > preinit_xen_time() could be splited so it can be moved just above
> > tasklet_subsys_init() after device tree is initialized but I don't think
> > there is to much sense for that.
> >
> > >    
> > >        /* set_xen_timer must have been set by sbi_init() already */
> > >        ASSERT(set_xen_timer);
> > The ASSERT is harmless, but NOW_good could technically go after it.
> "could" or do you perhaps even mean "should"? I'd like to keep the write
> next to that of boot_clock_cycles, but of course only if there's no
> dependency on set_xen_timer.
There is no dependency on set_xen_timer so feel free to keep the write 
next to that of boot_clock_cycles.
~ Oleksii