linux-kernel - Re: [PATCH v2 1/3] context_tracking: Split guest_enter/exit

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Message-ID: <CANRm+Cw=7kKztPFHaXrK926ve7pY3NN4O22t_QaevHnCXqX5tg@mail.gmail.com>
Date:   Tue, 13 Apr 2021 15:52:35 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Michael Tokarev <mjt@....msk.ru>
Subject: Re: [PATCH v2 1/3] context_tracking: Split guest_enter/exit_irqoff

On Tue, 13 Apr 2021 at 15:48, Christian Borntraeger
<borntraeger@...ibm.com> wrote:
>
>
>
> On 13.04.21 09:38, Wanpeng Li wrote:
> > On Tue, 13 Apr 2021 at 15:35, Christian Borntraeger
> > <borntraeger@...ibm.com> wrote:
> >>
> >>
> >>
> >> On 13.04.21 09:16, Wanpeng Li wrote:
> >> [...]
> >>
> >>> @@ -145,6 +155,13 @@ static __always_inline void guest_exit_irqoff(void)
> >>>    }
> >>>
> >>>    #else
> THis is the else part
>
>
> >>> +static __always_inline void context_guest_enter_irqoff(void)
> >>> +{
> >>> +     instrumentation_begin();
>
> 2nd on
> >>> +     rcu_virt_note_context_switch(smp_processor_id());
> >>> +     instrumentation_end();
> 2nd off
> >>> +}
> >>> +
> >>>    static __always_inline void guest_enter_irqoff(void)
> >>>    {
> >>>        /*
> >>> @@ -155,10 +172,13 @@ static __always_inline void guest_enter_irqoff(void)
> >>>        instrumentation_begin();
>
> first on
> >>>        vtime_account_kernel(current);
> >>>        current->flags |= PF_VCPU;
> >>> -     rcu_virt_note_context_switch(smp_processor_id());
> >>>        instrumentation_end();
>
> first off
> >>> +
> >>> +     context_guest_enter_irqoff();
> here we call the 2nd on and off.
> >>
> >> So we now do instrumentation_begin 2 times?
> >
> > Similar to context_guest_enter_irqoff() ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN.
>
> For the
> ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN part
> context_guest_enter_irqoff()
> does not have instrumentation_begin/end.
>
> Or did I miss anything.

I mean the if (!context_tracking_enabled_this_cpu()) part in the
function context_guest_enter_irqoff() ifdef
CONFIG_VIRT_CPU_ACCOUNTING_GEN. :)

    Wanpeng