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Re: [Xen-devel] [[PATCH for-4.13]] xen/arm: mm: Allow generic xen page-tables helpers to be called early


  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • From: Julien Grall <Julien.Grall@xxxxxxx>
  • Date: Mon, 7 Oct 2019 20:35:52 +0000
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  • Thread-topic: [[PATCH for-4.13]] xen/arm: mm: Allow generic xen page-tables helpers to be called early

Hi,

On 03/10/2019 02:02, Stefano Stabellini wrote:
> On Fri, 20 Sep 2019, Julien Grall wrote:
>> That's not correct. alloc_boot_pages() is actually here to allow dynamic
>> allocation before the memory subsystem (and therefore the runtime allocator)
>> is initialized.
> 
> Let me change the question then: is the system_state ==
> SYS_STATE_early_boot check strictly necessary? It looks like it is not:
> the patch would work even if it was just:

I had a few thoughts about it. On Arm32, this only really works for 
32-bits machine address (it can go up to 40-bits). I haven't really 
fully investigated what could go wrong, but it would be best to keep it 
only for early boot.

Also, I don't really want to rely on this "workaround" after boot. Maybe 
we would want to keep them unmapped in the future.

Cheers,

-- 
Julien Grall
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