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Re: [Xen-devel] [PATCH for-next 7/9] xen: Convert is_xen_heap_mfn to use typesafe MFN
- To: Julien Grall <julien.grall@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Thu, 14 Mar 2019 10:14:36 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
- Delivery-date: Thu, 14 Mar 2019 10:14:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 14/03/2019 10:12, Julien Grall wrote:
> Hi Jan,
>
> On 3/14/19 7:52 AM, Jan Beulich wrote:
>>>>> On 13.03.19 at 18:24, <julien.grall@xxxxxxx> wrote:
>>> On 13/03/2019 15:04, Jan Beulich wrote:
>>>>>>> On 18.02.19 at 12:35, <julien.grall@xxxxxxx> wrote:
>>>>> --- a/xen/common/page_alloc.c
>>>>> +++ b/xen/common/page_alloc.c
>>>>> @@ -2121,9 +2121,9 @@ void init_xenheap_pages(paddr_t ps, paddr_t pe)
>>>>> * Yuk! Ensure there is a one-page buffer between Xen and
>>>>> Dom zones, to
>>>>> * prevent merging of power-of-two blocks across the zone
>>>>> boundary.
>>>>> */
>>>>> - if ( ps && !is_xen_heap_mfn(paddr_to_pfn(ps)-1) )
>>>>> + if ( ps && !is_xen_heap_mfn(_mfn(paddr_to_pfn(ps)-1)) )
>>>>> ps += PAGE_SIZE;
>>>>> - if ( !is_xen_heap_mfn(paddr_to_pfn(pe)) )
>>>>> + if ( !is_xen_heap_mfn(maddr_to_mfn(pe)) )
>>>>
>>>> Why maddr_to_mfn() here but still paddr_to_pfn() above? Oh,
>>>> we don't have any mfn_sub(), I see.
>>>
>>> Yes we don't have mfn_sub() (or even gfn_sub()). I only found a
>>> couple of places
>>> where such helpers might be useful. I can introduce the 2 helpers if
>>> you think
>>> it is worth it.
>>
>> Well, I guess in the end I'm fine either way. It simply struck me
>> as odd at the first glance that you use maddr_to_mfn() in one
>> case but not the other.
>
> I wanted to avoid adding mfn_x(...) on the line:
>
> _mfn(mfn_x(maddr_to_mfn(ps)) - 1)
>
> I will look to introduce mfn_sub()/gfn_sub().
You do know that mfn_add(mfn, -1) will DTRT?
~Andrew
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