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Message-ID: <20201106004743.GA380136@tp-x1>
Date: Thu, 5 Nov 2020 19:47:43 -0500
From: Brian Masney <bmasney@...hat.com>
To: boris.ostrovsky@...cle.com, jgross@...e.com, sstabellini@...nel.org
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
hpa@...or.com, xen-devel@...ts.xenproject.org,
linux-kernel@...r.kernel.org, dustymabe@...hat.com
Subject: Re: [PATCH] x86/xen: fix warning when running with nosmt mitigations
On Thu, Nov 05, 2020 at 07:35:29PM -0500, Brian Masney wrote:
> diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
> index 799f4eba0a62..4a052459a08e 100644
> --- a/arch/x86/xen/spinlock.c
> +++ b/arch/x86/xen/spinlock.c
> @@ -93,9 +93,24 @@ void xen_init_lock_cpu(int cpu)
>
> void xen_uninit_lock_cpu(int cpu)
> {
> + int irq;
> +
> if (!xen_pvspin)
> return;
>
> + /*
> + * When booting the kernel with 'mitigations=auto,nosmt', the secondary
> + * CPUs are not activated and only the primary thread on each CPU core
> + * is used. In this situation, xen_hvm_smp_prepare_cpus(), and more
> + * importantly xen_init_lock_cpu(), is not called, so the
> + * lock_kicker_irq is not initialized for the secondary CPUs. Let's
> + * exit early if the irq is not set to avoid a warning in the console
> + * log.
> + */
> + irq = per_cpu(lock_kicker_irq, cpu);
> + if (irq == -1)
> + return;
> +
> unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
As soon as I saw this on lore, I saw that I should have passed the irq
variable to unbind_from_irqhandler() rather than doing another per_cpu()
lookup. I'll wait for feedback about the general approach before posting
a v2.
Brian
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