Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [v2 PATCH 4/4] x86/kvm: Add guest side support for virtual suspend time injection | Date | Tue, 10 Aug 2021 17:48:02 +0200 |
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On Fri, Aug 06 2021 at 19:07, Hikaru Nishida wrote: > arch/x86/Kconfig | 13 ++++++++++ > arch/x86/include/asm/idtentry.h | 4 +++ > arch/x86/include/asm/kvm_para.h | 9 +++++++ > arch/x86/kernel/kvmclock.c | 40 +++++++++++++++++++++++++++++ > include/linux/timekeeper_internal.h | 4 +++ > kernel/time/timekeeping.c | 33 ++++++++++++++++++++++++
Again, this wants to be split into infrastructure and usage.
> --- a/include/linux/timekeeper_internal.h > +++ b/include/linux/timekeeper_internal.h > @@ -124,6 +124,10 @@ struct timekeeper { > u32 ntp_err_mult; > /* Flag used to avoid updating NTP twice with same second */ > u32 skip_second_overflow; > +#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST > + /* suspend_time_injected keeps the duration injected through kvm */ > + u64 suspend_time_injected;
This is KVM only, so please can we have a name for that struct member which reflects this?
> +#endif > #ifdef CONFIG_DEBUG_TIMEKEEPING > long last_warning; > /*
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 3ac3fb479981..424c61d38646 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -2125,6 +2125,39 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset, > return offset; > } > > +#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST > +/* > + * timekeeping_inject_virtual_suspend_time - Inject virtual suspend time > + * when requested by the kvm host.
If this is an attempt to provide a kernel-doc comment for this function, then it's clearly a failed attempt and aside of that malformatted.
> + * This function should be called under irq context.
Why? There is no reason for being called from interrupt context and nothing inforces it.
> + */ > +void timekeeping_inject_virtual_suspend_time(void) > +{ > + /* > + * Only updates shadow_timekeeper so the change will be reflected > + * on the next call of timekeeping_advance().
No. That's broken.
timekeeping_inject_virtual_suspend_time();
do_settimeofday() or do_adjtimex()
timekeeping_update(tk, TK_MIRROR...);
and your change to the shadow timekeeper is gone.
Of course there is also no justification for this approach. What's wrong with updating it right away?
> + */ > + struct timekeeper *tk = &shadow_timekeeper; > + unsigned long flags; > + struct timespec64 delta; > + u64 suspend_time;
Please sort variables in reverse fir tree order and not randomly as you see fit.
> + > + raw_spin_lock_irqsave(&timekeeper_lock, flags); > + suspend_time = kvm_get_suspend_time(); > + if (suspend_time > tk->suspend_time_injected) { > + /* > + * Do injection only if the time is not injected yet. > + * suspend_time and tk->suspend_time_injected values are > + * cummrative, so take a diff and inject the duration.
cummrative?
> + */ > + delta = ns_to_timespec64(suspend_time - tk->suspend_time_injected); > + __timekeeping_inject_sleeptime(tk, &delta); > + tk->suspend_time_injected = suspend_time;
It's absolutely unclear how this storage and diff magic works and the comment is not helping someone not familiar with the implementation of kvm_get_suspend_time() and the related code at all. Please explain non-obvious logic properly.
Thanks,
tglx
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