Re: [Xen-devel] Regarding page table management changes from Xen v1 to Xen v2 (and v3)

[Himanshu Raj <rhim@xxxxxxxxxxxxx>]

> >Could you tell me another example other than fork when one can use 
> >batched PTE
> >modifications.
> 
> fork() is the only one for us these days. All others use 
> update_va_mapping(), act on pagetables that aren't pinned (so the guest 
> can directly update them without faulting) or are infrequent enough we 
> do not care.
Not sure I understand the last part (aren't pinned ...) - my assumptions about
page tables are (these apply to both direct mapped and shadow page tables):

1. Always pinned (backed) - so a access to them cannot cause a page unavailable 
fault.
2. Always read only to guest - so a read access to them is fine, but a write 
access
   will cause a protection fault.

Both of these faults are reflected as a PG fault.

Are you refering to the case when Xen has "detached" the page table page and
has made it RW for guest?

Thanks for your answers and patience :-).

-Himanshu

-- 
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Himanshu Raj
PhD Student, GaTech (www.cc.gatech.edu/~rhim)
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