linux-kernel - Re: [patch V6 10/37] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY

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Message-ID: <875zcpvk70.fsf@nanos.tec.linutronix.de>
Date:   Thu, 21 May 2020 09:08:51 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Andrew Cooper <andrew.cooper3@...rix.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...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 V6 10/37] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY

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

> On 5/20/20 3:16 PM, Thomas Gleixner wrote:
>
>
>> +__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
>> +{
>> +	struct pt_regs *old_regs;
>> +	bool inhcall;
>> +
>> +	idtentry_enter(regs);
>> +	old_regs = set_irq_regs(regs);
>> +
>> +	run_on_irqstack(__xen_pv_evtchn_do_upcall, NULL, regs);
>
>
> We need to handle nested case (i.e. !irq_needs_irq_stack(), like in your
> original version). Moving get_and_clear_inhcall() up should prevent
> scheduling when this happens.

I locally changed run_on_irqstack() to do the magic checks and select the
right one.

Thanks,

        tglx