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Date: Mon, 16 Jun 2014 17:37:10 +0100
From: David Vrabel <david.vrabel@citrix.com>
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To: Vitaly Kuznetsov <vkuznets@redhat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        David Vrabel <david.vrabel@citrix.com>
CC: <xen-devel@lists.xenproject.org>, Andrew Jones <drjones@redhat.com>,
        <x86@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH v2] xenpv: don't BUG when failing to setup
 NMI callback
References: <1402916820-27500-1-git-send-email-vkuznets@redhat.com>
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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