From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Chen, Tiejun" <tiejun.chen@intel.com>
Subject: Re: [v7][RFC][PATCH 08/13] xen/x86/p2m: set
 p2m_access_n for reserved device memory mapping
Date: Tue, 04 Nov 2014 19:51:49 +0800
Message-ID: <5458BDD5.8070800@intel.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: yang.z.zhang@intel.com, kevin.tian@intel.com, tim@xen.org, xen-devel@lists.xen.org
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On 2014/11/4 19:41, Jan Beulich wrote:
>>>> On 04.11.14 at 11:41, <tiejun.chen@intel.com> wrote:
>> On 2014/11/4 16:02, Jan Beulich wrote:
>>>>>> On 04.11.14 at 02:35, <tiejun.chen@intel.com> 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.

Yeah, this also makes sense.

Thanks
Tiejun