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

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Date:   Tue, 13 Apr 2021 09:48:32 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Wanpeng Li <kernellwp@...il.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 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.