Re: [Xen-devel] Switching from writeable pagetable to shadowlog-dirtyat runtime

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 14 Oct 2005, at 03:46, Li, Chengyuan wrote:

> I don't see ptwr_flush() when shadow mode enable in both ia32 and 
> x86_64 code. Why plain ia32 log dirty shadow can work?
Perhaps it can't, properly. :-)

The best fix will be to make domain_pause() call 
sync_pagetable_state(d). The main problem I can see is that the 
cleanup_writeable_pagetable() function is not currently safe to be 
called by other than the subject domain. For example, failure paths 
crash the calling domain rather than the subject domain! This needs 
fixing.
> audit_adjust_pgtables() is for plain ia32 only and it doesn't work for 
> both ia32 pae and x86_64, but this function only check the ref counts 
> and doesn't update guest PTE entry, e.g. R/W bit.
> Another question is that how does guest update its guest page-table 
> after shadow mode is enabled?  As writable-pagetable can't be used 
> after shadow mode is enabled.
Shadow pagetable code has its own quite separate writeable pagetable 
logic, I believe. Which is why the non-shadow wrpt state must be 
flushed before switching to shadow pagetables.
 -- Keir


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