Re: [Xen-devel] Re: how to enable shadow page table? Do I havetorun HVM guest systems for shadow paging mode?

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

Hi,

At 15:55 +0000 on 19 Mar (1237478115), Long Wang wrote:
> I am a little confused. You wrote: 
> 1) "The dirty bit of a *shadow* PTE is usually set by _sh_propagate (since
> we don't care about it) except for some optimizations to do with HVM video
> RAM mappings, where it's set by the MMU." 
> 
> 2) "Only for the *shadow* PTE, since that's the only one the MMU ever
> Sees". 
> 
> Do you mean that most of *shadow* PTE dirty bits (in PV) are set by
> _sh_propagate() (through a read-only-bit-triggered interception)?

No, I mean that when _sh_propagate() makes a shadow PTE that has the R/W
bit set, it usually sets the Dirty bit as well (to save the MMU the
extra write cycle later).

Cheers,

Tim.

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

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