linux-kernel - Re: [PATCH] xenpv: don't BUG when failing to setup NMI callback

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Message-ID: <539AFD6D.40204@citrix.com>
Date:	Fri, 13 Jun 2014 14:32:29 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	<x86@...nel.org>, <xen-devel@...ts.xenproject.org>,
	<linux-kernel@...r.kernel.org>, Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH] xenpv: don't BUG when failing to setup NMI callback

On 13/06/14 12:26, Vitaly Kuznetsov wrote:
> 
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -593,8 +593,17 @@ void xen_enable_syscall(void)
>  void xen_enable_nmi(void)
>  {
>  #ifdef CONFIG_X86_64
> -	if (register_callback(CALLBACKTYPE_nmi, (char *)nmi))
> +	int ret;
> +
> +	ret = register_callback(CALLBACKTYPE_nmi, (char *)nmi);
> +	if (ret == -EINVAL) {
> +		/* Hypervisor probably forbids us to register NMI callback,
> +		   that is expected when running on top of Xen-3.1 and older */
> +		pr_warn("xen: failed to register NMI callback\n");
> +	} else if (ret != 0) {
> +		/* Other hypervisor failure */
>  		BUG();

I don't think we ever want to BUG() if this hypercall fails.  Just print
a warning.

David
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