linux-kernel - Re: [RESEND][patch V3 19/23] x86/kvm/vmx: Add hardirq tracing to guest enter/exit

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Message-ID: <87o8slz6d9.fsf@nanos.tec.linutronix.de>
Date:   Wed, 25 Mar 2020 00:21:38 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Paul McKenney <paulmck@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Joel Fernandes \(Google\)" <joel@...lfernandes.org>,
        "Steven Rostedt \(VMware\)" <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RESEND][patch V3 19/23] x86/kvm/vmx: Add hardirq tracing to guest enter/exit

Peter Zijlstra <peterz@...radead.org> writes:

> On Fri, Mar 20, 2020 at 07:00:15PM +0100, Thomas Gleixner wrote:
>> The VMX code does not track hard interrupt state correctly. The state in
>> tracing and lockdep is 'OFF' all the way during guest mode. From the host
>> point of view this is wrong because the VMENTER reenables interrupts like a
>> return to user space and VMENTER disables them again like an entry from
>> user space.
>> 
>> Make it do exactly the same thing as enter/exit user mode does.
>> 
>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>
> This patch (and the SVM counterpart) result in:
>
> ERROR: "lockdep_hardirqs_on" [arch/x86/kvm/kvm-amd.ko] undefined!
> ERROR: "lockdep_hardirqs_off" [arch/x86/kvm/kvm-amd.ko] undefined!
> ERROR: "__trace_hardirqs_off" [arch/x86/kvm/kvm-amd.ko] undefined!
> ERROR: "lockdep_hardirqs_on_prepare" [arch/x86/kvm/kvm-amd.ko] undefined!
> ERROR: "__trace_hardirqs_on" [arch/x86/kvm/kvm-amd.ko] undefined!
> ERROR: "lockdep_hardirqs_on" [arch/x86/kvm/kvm-intel.ko] undefined!
> ERROR: "lockdep_hardirqs_off" [arch/x86/kvm/kvm-intel.ko] undefined!
> ERROR: "__trace_hardirqs_off" [arch/x86/kvm/kvm-intel.ko] undefined!
> ERROR: "lockdep_hardirqs_on_prepare" [arch/x86/kvm/kvm-intel.ko] undefined!
> ERROR: "__trace_hardirqs_on" [arch/x86/kvm/kvm-intel.ko] undefined!
>
> on allmodconfig.
>
> I suppose them things need an EXPORT_SYMBOL_GPL() on them.

Indeed.