From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v18 11/16] x86/VPMU: Handle PMU interrupts
	for PV guests
Date: Tue, 17 Feb 2015 12:41:44 -0500
Message-ID: <54E37D58.1000202@oracle.com>
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To: Andrew Cooper <andrew.cooper3@citrix.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 02/17/2015 10:44 AM, Andrew Cooper wrote:
> 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.

IIRC Jan asked for d->vcpu tests at some point. This particular one is 
probably indeed pointless since hardware_domain better have this as 
non-NULL.

-boris


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