linux-kernel - Re: [Xen-devel] [PATCH v2] xenpv: don't BUG when failing to setup NMI callback

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Message-ID: <539F1D36.5040008@citrix.com>
Date:	Mon, 16 Jun 2014 17:37:10 +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>,
	David Vrabel <david.vrabel@...rix.com>
CC:	<xen-devel@...ts.xenproject.org>,
	Andrew Jones <drjones@...hat.com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH v2] xenpv: don't BUG when failing to setup
 NMI callback

On 16/06/14 12:07, Vitaly Kuznetsov wrote:
> 
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -746,12 +746,13 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
>  		 */
>  		;
>  #endif
> -	} else if (addr == (unsigned long)nmi)
> +	} else if (addr == (unsigned long)nmi) {
>  		/*
> -		 * Use the native version as well.
> +		 * Use the native version as well but require Xen >= 3.2
>  		 */
> -		;
> -	else {
> +		if (!xen_running_on_version_or_later(3, 2))
> +			return 0;
> +	} else {

The end result of this looked odd so I played around with it a bit and
it turns out that the register_callback for the NMI is entirely unneeded
(since we set the NMI callback via the write_idt pv-op and it's also
broken since it only sets the callback on the current VCPU.

I'm preparing an alternate patch, but I do not have a Xen 3.1 install I
can test with.

David
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