Re: [Xen-devel] relationship of the auto_translated_physmap feature and the shadow_mode_translate mode of domain

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 22:45 +0800 on 30 May (1212187536), HuYanyan wrote:
>     What I want to know is whether there are some relationship between the
> auto_translated_physmap feature and the shadow_mode_translate mode of
> domain, do they have the same meaning?

They have almost the same meaning.  shadow_mode_translate means that 
the domain is using shadow pagetables and that the shadow pagetable code
is responsible for handling the translation from guest-physical to
machine-physical addresses.  HVM guests always run in this mode; by
default, PV guests don't run under shadow pagetables at all, except
during live migration, and even then they do their own translation.

auto_translated_physmap is a PV guest feature flag that requires the
guest to be run in shadow_mode_translate.

BUT: the code for running PV guests in shadow_mode_translate does not
work, as far as I know.  The last time anyone tried to make the
xen-unstable shadow code work in this configuration was more than a year
ago.

> I think this feature will work(Guest
> kernel do the p2m and m2p translation) only when the shadow mode of domain
> is enabled, but this is not true for domain0 because it's a paravirtualized
> domain, why did it still declare this feature? 

It was useful for some research projects to be able to change the p2m
without altering the guest's state, when doing things like execution
replay.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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