Question about EPT translation

Question about EPT translation

[confucius]

Hi,everyone. I have some questions.
1. Does hvmoader need EPT for address translation when it  is running?
2. I am sure the guest kernel need EPT when running, but not sure whether
hvmloader also needs. I think  when virtual bios in hvmloader running, we
should make virtual bios sees as if the memory starting from 0, so hvmloader
needs EPT, am I right?
3. If hvmloader needs EPT, where we construct EPT structure for it? I can't
find correlative part  in code flow.
Any helps?

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Re: Question about EPT translation

[Daniel Castro]

Hello,
Next time I will only replay through the list. CC the list

2011/5/29 henanwxr <henanwxr@hotmail.com>:
> Hi Daniel, I have post my questions on xen-devel but nobody reply. So I turn
> to you for help.
> 1. Does hvmoader need EPT for address translation when it  is running?
If you are talking to pure HVM Guest then yes.
> 2. I am sure the guest kernel need EPT when running, but not sure whether
> hvmloader also needs. I think  when virtual bios in hvmloader running, we
> should make virtual bios sees as if the memory starting from 0, so hvmloader
> needs EPT, am I right?
Yes
> 3. If hvmloader needs EPT, where we construct EPT structure for it? I can't
> find correlative part  in code flow.
The address translation is not done by hvmloader, hvmloader is only
used to deploy data to memory, the translation is done via Hypervisor
aided by hardware.



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| |   | Daniel Castro,                |
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Re: Question about EPT translation

[Tim Deegan]

Hi,

At 09:17 -0700 on 27 May (1306487843), confucius wrote:
> Hi,everyone. I have some questions.
> 1. Does hvmoader need EPT for address translation when it  is running?

_All_ HVM guests need _either_ EPT/NPT _or_ shadow pagetables, to make
the extra translation from guest physical addresses to machine addresses.

> 3. If hvmloader needs EPT, where we construct EPT structure for it? I can't
> find correlative part  in code flow.

Did you try searching the code for "EPT"?  The EPT datastructures are
construced in p2m_ept.c.  (p2m is the general term in Xen for the table
that maps physical addresses to machine addresses).

Tim.

-- 
                                         Tim Deegan <tjd@phlegethon.org>
                We were back to the sad age-old knowledge that there are
                       only two genuine aphrodisiacs: youth and boredom.
                      [ Alistair Cooke, "Letter From America", 12/5/98 ]