From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [V10 PATCH 0/4] pvh dom0 patches...
Date: Thu, 08 May 2014 16:20:39 +0100
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To: =?UTF-8?Q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>
Cc: George.Dunlap@eu.citrix.com, xen-devel@lists.xenproject.org, keir.xen@gmail.com, tim@xen.org
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>>> On 08.05.14 at 17:00, <roger.pau@citrix.com> wrote:
> On 08/05/14 12:44, Jan Beulich wrote:
>>>>> On 08.05.14 at 12:27, <roger.pau@citrix.com> wrote:
>>> On 07/05/14 13:34, Jan Beulich wrote:
>>>>>>> On 07.05.14 at 11:48, <roger.pau@citrix.com> wrote:
>>>>> +    /* Clamp e820 memory map to match the memory assigned to Dom0 */
>>>>> +    for ( i = 0, entry = d->arch.e820; i < d->arch.nr_e820; i++, entry++ )
>>>>> +    {
>>>>> +        if ( entry->type != E820_RAM )
>>>>> +            continue;
>>>>> +
>>>>> +        if ( nr_pages == cur_pages )
>>>>> +        {
>>>>> +            /*
>>>>> +             * We already have all the assigned memory,
>>>>> +             * mark this region as reserved.
>>>>> +             */
>>>>> +            entry->type = E820_RESERVED;
>>>>
>>>> That seems undesirable, as it will prevent Linux from using that space
>>>> for MMIO purposes. Plus keeping the region here is consistent with
>>>> simply shrinking the range below (yielding the remainder uncovered
>>>> by any E820 entry). I think you ought to zap the entry here.
>>>
>>> I don't think this regions can be used for MMIO, the gpfns in the guest
>>> p2m are not set as p2m_mmio_direct.
>> 
>> Not at the point you build the domain, but such a use can't and
>> shouldn't be precluded ones the domain is up.
> 
> OK, setting entry.size = 0 should work.

Please just remove unused entries altogether. You never know
whether some OS can't deal with zero-size ones. And keeping the
number of table entries low is generally also desirable.

Jan