Re: [Xen-devel] [PATCH v12 for-xen-4.5 12/20] x86/VPMU: Initialize PMU for PV(H) guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.09.14 at 18:04, <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 09/29/2014 11:42 AM, Jan Beulich wrote:
>>>>> On 29.09.14 at 17:41, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> On 09/29/2014 11:25 AM, Jan Beulich wrote:
>>>>>>> On 25.09.14 at 21:28, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>>> @@ -389,14 +390,26 @@ static int amd_vpmu_initialise(struct vcpu *v)
>>>>>            }
>>>>>        }
>>>>>    
>>>>> -    ctxt = xzalloc_bytes(sizeof(struct xen_pmu_amd_ctxt) +
>>>>> -                         2 * sizeof(uint64_t) * AMD_MAX_COUNTERS);
>>>>> -    if ( !ctxt )
>>>>> +    regs_size = 2 * sizeof(uint64_t) * AMD_MAX_COUNTERS;
>>>>> +    if ( is_hvm_domain(v->domain) )
>>>>>        {
>>>>> -        gdprintk(XENLOG_WARNING, "Insufficient memory for PMU, "
>>>>> -            " PMU feature is unavailable on domain %d vcpu %d.\n",
>>>>> -            v->vcpu_id, v->domain->domain_id);
>>>>> -        return -ENOMEM;
>>>>> +        ctxt = xzalloc_bytes(sizeof(struct xen_pmu_amd_ctxt) + 
>>>>> regs_size);
>>>>> +        if ( !ctxt )
>>>>> +        {
>>>>> +            gdprintk(XENLOG_WARNING, "Insufficient memory for PMU, "
>>>>> +                "PMU feature is unavailable\n");
>>>>> +            return -ENOMEM;
>>>>> +        }
>>>>> +    }
>>>>> +    else
>>>>> +    {
>>>>> +        if ( sizeof(struct xen_pmu_data) + regs_size > PAGE_SIZE )
>>>> This is a compile time constant condition - no reason to issue a
>>>> message and return failure at runtime, just BUILD_BUG_ON() instead.
>>> It will not be if I replace AMD_MAX_COUNTERS with runtime register
>>> count, as you asked in an earlier comment.
>> For which case see the respective VMX side comment.
> 
> Not sure I understand what you mean here. it will be almost exactly the 
> same.

I said on the respective VMX code that issuing the message
repeatedly at normal runtime is pointless - it suffices to issue it
once during boot.

Jan


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