Re: [Xen-devel] [v7][RFC][PATCH 08/13] xen/x86/p2m: set p2m_access_n for reserved device memory mapping

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.11.14 at 11:41, <tiejun.chen@xxxxxxxxx> wrote:
> On 2014/11/4 16:02, Jan Beulich wrote:
>>>>> On 04.11.14 at 02:35, <tiejun.chen@xxxxxxxxx> wrote:
>>> @@ -686,8 +686,25 @@ guest_physmap_add_entry(struct domain *d, unsigned 
>>> long gfn,
>>>        /* Now, actually do the two-way mapping */
>>>        if ( mfn_valid(_mfn(mfn)) )
>>>        {
>>> -        rc = p2m_set_entry(p2m, gfn, _mfn(mfn), page_order, t,
>>> -                           p2m->default_access);
>>> +        rc = 0;
>>> +        a =  p2m->default_access;
>>> +        if ( !is_hardware_domain(d) )
>>> +        {
>>> +            rc = 
>>> iommu_get_reserved_device_memory(p2m_check_reserved_device_memory,
>>> +                                                  &gfn);
>>> +            /* We always avoid populating reserved device memory. */
>>> +            if ( rc == 1 )
>>> +                goto out;
>>
>> But you'll need to make sure that you don't return 1 to the callers:
> 
> You're right.
> 
>> They expect 0 or negative error codes. But with the model of
>> not even populating these regions (or relocating the memory
>> before [at boot time] assigning a device associated with an RMRR)
>> I think this needs to become an error anyway.
> 
> Looks -EINVAL might be used.

Hmm, -EINVAL is being used way too frequently already. -EBUSY
would make it at least a little bit more distinct.

Jan


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