linux-kernel - Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual suspend time injection

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Date:   Tue, 10 Aug 2021 17:21:05 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Hikaru Nishida <hikalium@...omium.org>,
        linux-kernel@...r.kernel.org, dme@....org, mlevitsk@...hat.com
Cc:     suleiman@...gle.com, Hikaru Nishida <hikalium@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        John Stultz <john.stultz@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual
 suspend time injection

On Fri, Aug 06 2021 at 19:07, Hikaru Nishida wrote:

> This patch implements virtual suspend time injection support for kvm

git grep 'This patch' Documentation/process/

> hosts.
>
> If this functionality is enabled and the guest requests it, the host
> will stop all the clocks observed by the guest during the host's
> suspension and report the duration of suspend to the guest through
> struct kvm_host_suspend_time to give a chance to adjust CLOCK_BOOTTIME
> to the guest. This mechanism can be used to align the guest's clock
> behavior to the hosts' ones.
>
> Signed-off-by: Hikaru Nishida <hikalium@...omium.org>
> ---
>
>  arch/x86/include/asm/kvm_host.h |   5 ++
>  arch/x86/kvm/Kconfig            |  13 ++++
>  arch/x86/kvm/cpuid.c            |   4 ++
>  arch/x86/kvm/x86.c              | 109 +++++++++++++++++++++++++++++++-
>  include/linux/kvm_host.h        |   8 +++
>  kernel/time/timekeeping.c       |   3 +

Please split this into adding the infrastructure and then implementing
the x86 side of it.

>  
> +#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING
> +void kvm_arch_timekeeping_inject_sleeptime(const struct timespec64 *delta);
 +#else
 +static inline void kvm_arch_timekeeping_inject_sleeptime(const struct timespec64 *delta){}
> +#endif /* CONFIG_KVM_VIRT_SUSPEND_TIMING */
> +
>  #endif
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 233ceb6cce1f..3ac3fb479981 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1797,6 +1797,9 @@ void timekeeping_resume(void)
>  	if (inject_sleeptime) {
>  		suspend_timing_needed = false;
>  		__timekeeping_inject_sleeptime(tk, &ts_delta);
> +#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING
> +		kvm_arch_timekeeping_inject_sleeptime(&ts_delta);
> +#endif

which get's rid of these ugly ifdefs.

Also this is the wrong place because sleep time can be injected from
other places as well. This should be in __timekeeping_inject_sleeptime()
if at all.

Thanks,

        tglx