linux-kernel - Re: [patch V5 24/38] x86/entry: Provide IDTENTRY

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Message-ID: <87a729y400.fsf@nanos.tec.linutronix.de>
Date:   Fri, 15 May 2020 10:52:15 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Wei Liu <wei.liu@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Jason Chen CJ <jason.cj.chen@...el.com>,
        Zhao Yakui <yakui.zhao@...el.com>,
        "Peter Zijlstra \(Intel\)" <peterz@...radead.org>
Subject: Re: [patch V5 24/38] x86/entry: Provide IDTENTRY_SYSVEC

Boris Ostrovsky <boris.ostrovsky@...cle.com> writes:

> On 5/12/20 5:01 PM, Thomas Gleixner wrote:
>> +
>> +/**
>> + * DEFINE_IDTENTRY_SYSVEC - Emit code for system vector IDT entry points
>> + * @func:	Function name of the entry point
>> + *
>> + * idtentry_enter/exit() and irq_enter/exit_rcu() are invoked before the
>> + * function body. KVM L1D flush request is set.
>
>
> This is used for entry points for Xen and hyperV as well. Even though
> it's harmless at the moment, do we still want to set this flag for non-KVM?

Right, it's pointless for !KVM, but we have set this unconditionally
since the l1tf mess was introduced. I'm not sure whether it's worth to
optimize the single store out.

Thanks,

        tglx