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Re: [Xen-devel] [PATCH] x86: Get rid of p2m_host array allocation for HVM guests


  • To: Julien Grall <julien.grall@xxxxxxx>, Varad Gautam <vrd@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Thu, 11 Jul 2019 09:25:57 -0500
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Amit Shah <aams@xxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, David Woodhouse <dwmw@xxxxxxxxxxxx>
  • Delivery-date: Thu, 11 Jul 2019 14:26:15 +0000
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On 10/07/2019 14:25, Julien Grall wrote:
>>
>> However, in attempting to review this, I've got some bigger questions.
>>
>> All ARM and x86 HVM (and PVH) guests return true for
>> xc_dom_translated(), so should take the fastpath out of xc_dom_p2m() and
>> never read from dom->p2m_host[].  Therefore, I don't see why the
>> majority of this patch is necessary.
>
> I agree that p2m_host will never get used by Arm. So this is a waste
> of memory.
>
>>   On the ARM side, this also means
>> that dom->rambase_pfn isn't being used as intended, which suggests there
>> is further cleanup/correction to be done here.
>
> I am not sure to follow this. Could you expand it?

dom->rambase_pfn was introduced for ARM, and the code which uses it in
xc_dom_p2m() is dead (on ARM, not on x86).

It isn't functioning as intended.

~Andrew

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