linux-kernel - Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

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Message-ID: <5474BE7C.5040909@redhat.com>
Date:	Tue, 25 Nov 2014 18:38:04 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org
Subject: Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe



On 25/11/2014 18:21, Marcelo Tosatti wrote:
> +
> +	if (r == HRTIMER_RESTART) {
> +		do {
> +			ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
> +			if (ret == -ETIME)
> +				hrtimer_add_expires_ns(&ktimer->timer,
> +							ktimer->period);

Is it possible to just compute the time where the next interrupt
happens?  I suspect the printk and WARN_ON below can be easily triggered
by a guest.

Paolo

> +			i++;
> +		} while (ret == -ETIME && i < 10);
> +
> +		if (ret == -ETIME) {
> +			printk(KERN_ERR "%s: failed to reprogram timer\n",
> +			       __func__);
> +			WARN_ON(1);
> +		}
> +	}

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