Re: [PATCH v23 12/15] x86/VPMU: Handle PMU interrupts for PV(H) guests

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 06/05/2015 12:09 PM, Jan Beulich wrote:
>> @@ -201,27 +202,56 @@ static inline void context_load(struct vcpu *v)
>>       }
>>   }
>>   
>> -static void amd_vpmu_load(struct vcpu *v)
>> +static int amd_vpmu_load(struct vcpu *v, bool_t from_guest)
>>   {
>>       struct vpmu_struct *vpmu = vcpu_vpmu(v);
>> -    struct xen_pmu_amd_ctxt *ctxt = vpmu->context;
>> -    uint64_t *ctrl_regs = vpmu_reg_pointer(ctxt, ctrls);
>> +    struct xen_pmu_amd_ctxt *ctxt;
>> +    uint64_t *ctrl_regs;
>> +    unsigned int i;
>>   
>>       vpmu_reset(vpmu, VPMU_FROZEN);
>>   
>> -    if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
>> +    if ( !from_guest && vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
>>       {
>> -        unsigned int i;
>> +        ctxt = vpmu->context;
>> +        ctrl_regs = vpmu_reg_pointer(ctxt, ctrls);
>>   
>>           for ( i = 0; i < num_counters; i++ )
>>               wrmsrl(ctrls[i], ctrl_regs[i]);
>>   
>> -        return;
>> +        return 0;
>> +    }
>> +
>> +    if ( from_guest )
>> +    {
>> +        unsigned int num_enabled = 0;
>> +
>> +        ASSERT(!is_hvm_vcpu(v));
>> +
>> +        ctxt = &vpmu->xenpmu_data->pmu.c.amd;
>> +        ctrl_regs = vpmu_reg_pointer(ctxt, ctrls);
>> +        for ( i = 0; i < num_counters; i++ )
>> +        {
>> +            if ( (ctrl_regs[i] & CTRL_RSVD_MASK) != ctrl_rsvd[i] )
>> +                return -EINVAL;
>> +
>> +            if ( is_pmu_enabled(ctrl_regs[i]) )
>> +                num_enabled++;
>> +        }
>> +
>> +        if ( num_enabled )
>> +            vpmu_set(vpmu, VPMU_RUNNING);
>> +        else
>> +            vpmu_reset(vpmu, VPMU_RUNNING);
>> +
>> +        memcpy(vpmu->context, &vpmu->xenpmu_data->pmu.c.amd, ctxt_sz);
> For one, why don't you use ctxt here? And then I think I made very
> clear that all shared data must be read exactly once during any
> hypervisor operation. Yet afaict you do two reads (one in the
> verification loop above, and another in the memcpy()).


Yes, and this is what is done on Intel side as well. I will need to copy 
first then and verifiy the copied context.

-boris