From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v14 for-xen-4.5 13/21] x86/VPMU: Initialize
 PMU for PV(H) guests
Date: Mon, 27 Oct 2014 15:21:38 -0400
Message-ID: <544E9B42.5090207@oracle.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: kevin.tian@intel.com, keir@xen.org, suravee.suthikulpanit@amd.com, andrew.cooper3@citrix.com, tim@xen.org, dietmar.hahn@ts.fujitsu.com, xen-devel@lists.xen.org, Aravind.Gopalakrishnan@amd.com, jun.nakajima@intel.com, dgdegra@tycho.nsa.gov
List-Id: xen-devel@lists.xenproject.org

On 10/27/2014 12:38 PM, Jan Beulich wrote:
>
>> +static void pvpmu_finish(struct domain *d, xen_pmu_params_t *params)
>> +{
>> +    struct vcpu *v;
>> +    uint64_t mfn;
>> +
>> +    if ( (params->vcpu >= d->max_vcpus) || (d->vcpu == NULL) ||
>> +         (d->vcpu[params->vcpu] == NULL) )
>> +        return;
>> +
>> +    v = d->vcpu[params->vcpu];
>> +    if ( v != current )
>> +        vcpu_pause(v);
>> +
>> +    if ( v->arch.vpmu.xenpmu_data )
>> +    {
>> +        mfn = domain_page_map_to_mfn(v->arch.vpmu.xenpmu_data);
>> +        ASSERT(mfn != 0);
>> +        unmap_domain_page_global(v->arch.vpmu.xenpmu_data);
>> +        put_page_and_type(mfn_to_page(mfn));
> I think you absolutely need to clear v->arch.vpmu.xenpmu_data
> here, or else another call will (likely) crash the hypervisor. Even
> more, I think this actually needs serialization (and pvpmu_init() as
> well), especially with ...

What I should do is to destroy vpmu *before* everything else. And add 
tests for VPMU_CONTEXT_ALLOCATED at a couple of entry points to 
arch-specific code (I will need to rework Intel VPMU allocation to 
happen at initialization time as opposed to current lazy allocation). 
Then noone will be touching xenpmu_data whine it's not available. 
Including pvpmu_init().

-boris

>
>> --- a/xen/include/xsm/dummy.h
>> +++ b/xen/include/xsm/dummy.h
>> @@ -665,6 +665,9 @@ static XSM_INLINE int xsm_pmu_op (XSM_DEFAULT_ARG struct
>> domain *d, int op)
>>       case XENPMU_feature_set:
>>       case XENPMU_feature_get:
>>           return xsm_default_action(XSM_PRIV, d, current->domain);
>> +    case XENPMU_init:
>> +    case XENPMU_finish:
>> +        return xsm_default_action(XSM_HOOK, d, current->domain);
> ... this being XSM_HOOK rather than XSM_TARGET.
>
> Jan
>