linux-kernel - Re: [PATCH v4 02/17] x86/acrn: Introduce acrn_{setup, remove}_intr

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Date:   Tue, 29 Sep 2020 20:01:23 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     shuo.a.liu@...el.com
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yu Wang <yu1.wang@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Yakui Zhao <yakui.zhao@...el.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Fengwei Yin <fengwei.yin@...el.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>
Subject: Re: [PATCH v4 02/17] x86/acrn: Introduce acrn_{setup,
 remove}_intr_handler()

On Tue, Sep 22, 2020 at 07:42:56PM +0800, shuo.a.liu@...el.com wrote:
> +void acrn_setup_intr_handler(void (*handler)(void))
> +{
> +	acrn_intr_handler = handler;
> +}
> +EXPORT_SYMBOL_GPL(acrn_setup_intr_handler);
> +
> +void acrn_remove_intr_handler(void)
> +{
> +	acrn_intr_handler = NULL;
> +}
> +EXPORT_SYMBOL_GPL(acrn_remove_intr_handler);

I don't like this one bit.

Also, what stops the module from doing acrn_remove_intr_handler()
while it gets a HYPERVISOR_CALLBACK_VECTOR interrupt and the handler
disappearing from under it?

IOW, this should be an atomic notifier instead.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette