Re: [Xen-devel] [PATCH v7 12/19] x86/VPMU: Initialize PMU for PV guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.06.14 at 14:49, <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 06/11/2014 06:20 AM, Jan Beulich wrote:
>>>>> On 06.06.14 at 19:40, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> Code for initializing/tearing down PMU for PV guests
>>> ...
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -4031,7 +4031,8 @@ static hvm_hypercall_t *const 
> pvh_hypercall64_table[NR_hypercalls] = {
>>>       [ __HYPERVISOR_physdev_op ]      = (hvm_hypercall_t *)hvm_physdev_op,
>>>       HYPERCALL(hvm_op),
>>>       HYPERCALL(sysctl),
>>> -    HYPERCALL(domctl)
>>> +    HYPERCALL(domctl),
>>> +    HYPERCALL(xenpmu_op)
>> How is this change related to the subject and description?
> 
> Yes, this is result of my eliminating PVH patch as a standalone one and 
> spreading its content over other patches. I'll update the text.
> 
>>
>>> +static int pvpmu_init(struct domain *d, xen_pmu_params_t *params)
>>> +{
>>> +    struct vcpu *v;
>>> +    struct page_info *page;
>>> +    uint64_t gfn = params->d.val;
>>> +
>>> +    if ( !params || params->vcpu >= d->max_vcpus )
>>> +        return -EINVAL;
>>> +
>>> +    page = get_page_from_gfn(d, gfn, NULL, P2M_ALLOC);
>>> +    if ( !page )
>>> +        return -EINVAL;
>>> +
>>> +    if ( !get_page_type(page, PGT_writable_page) )
>>> +    {
>>> +        put_page(page);
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    v = d->vcpu[params->vcpu];
>> I'm sure I asked this before - what guarantees (now as well as
>> going forward) that you get non-NULL here? Various existing
>> code paths properly verify both d->vcpu and d->vcpu[...] not
>> being NULL, so you should do this consistently too.
> 
> Ah, I thought you were referring to params check last time. I'll add 
> vcpu checks as well.

And drop checking param against NULL - I don't think that check
makes any sense.

Jan


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