Page fault handling in vpagetable area clarification

Aggelos Economopoulos aoiko at
Sat Feb 10 08:50:01 PST 2007

On Saturday 10 February 2007 00:11, Matthew Dillon wrote:
>    In anycase, I think doing a technical article is a great idea and please
>    feel free to ask as many questions as you like, either in private mail
>    or on this kernel list.  I would love to get more information about the
>    VKERNEL's design out to the wider world :-)

I'll keep the technical questions public so that web searches can find them.

In vm_fault_object(), fs.prot gets downgraded unconditionally if this is a 
VM_MAPTYPE_VPAGETABLE entry. But if this was a write fault, 
vm_fault_vpagetable() has already set VPTE_M (and if the vkernel clears it, 
its pmap_clearbit() will invalidate the real kernel's pagetables). Why can't 
the protection stay RW in this case?


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