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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Andy Lutomirski <luto@kernel.org>
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        "Peter Zijlstra \(Intel\)" <peterz@infradead.org>
Subject: Re: [patch V6 10/37] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY
In-Reply-To: <3a1eb682-948e-aaa9-bda0-0e99152ed623@oracle.com>
References: <20200515234547.710474468@linutronix.de> <20200515235125.425810667@linutronix.de> <CALCETrUqK6hv4AuGL=GtK+12TCmr5nBA7CBy=X7TNA=w_Jk0Qw@mail.gmail.com> <87imgr7nwp.fsf@nanos.tec.linutronix.de> <CALCETrW4BxfTVzv8mXntNXiAPnKxqdMEv7djUknGZcrno2WJHg@mail.gmail.com> <87y2pm4ruh.fsf@nanos.tec.linutronix.de> <CALCETrUvH5DQvL6Lo6EkM04pr7wWj+7eZbTg3H_eLNXcZsH0FA@mail.gmail.com> <CALCETrX4Zy2iuc39XTifYd_mvezCEUtW2ax3=ec1TF=yZxAHDg@mail.gmail.com> <871rnewh5w.fsf@nanos.tec.linutronix.de> <3a1eb682-948e-aaa9-bda0-0e99152ed623@oracle.com>
Date:   Thu, 21 May 2020 09:08:51 +0200
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Boris Ostrovsky <boris.ostrovsky@oracle.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