From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v18 11/16] x86/VPMU: Handle PMU interrupts
	for PV guests
Date: Tue, 17 Feb 2015 15:44:27 +0000
Message-ID: <54E361DB.80408@citrix.com>
References: <1424125619-10851-1-git-send-email-boris.ostrovsky@oracle.com>
	<1424125619-10851-12-git-send-email-boris.ostrovsky@oracle.com>
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To: Boris Ostrovsky <boris.ostrovsky@oracle.com>, JBeulich@suse.com, kevin.tian@intel.com, suravee.suthikulpanit@amd.com, Aravind.Gopalakrishnan@amd.com, dietmar.hahn@ts.fujitsu.com, dgdegra@tycho.nsa.gov
Cc: tim@xen.org, jun.nakajima@intel.com, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

On 16/02/15 22:26, Boris Ostrovsky wrote:
> diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
> index 1d5ae8d..cf4c70b 100644
> --- a/xen/arch/x86/hvm/vpmu.c
> +++ b/xen/arch/x86/hvm/vpmu.c
>
> +static struct vcpu *choose_hwdom_vcpu(void)
> +{
> +    unsigned idx = smp_processor_id() % hardware_domain->max_vcpus;
> +
> +    if ( hardware_domain->vcpu == NULL )
> +        return NULL;

If d->vcpu is NULL, d->max_vcpus was 0 and you have already died with a #DE

You can guarentee that if max_vcpus > 0, d->vcpu is not NULL.

~Andrew

> +
> +    return hardware_domain->vcpu[idx];
> +}
> +