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Re: [Xen-devel] page fault handling in Xen

  • To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
  • From: jeet <jeet_sat12@xxxxxxxxxxx>
  • Date: Tue, 6 Mar 2007 18:46:17 +0530 (IST)
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 06 Mar 2007 05:15:22 -0800
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

>Above code will execute and in inner unlikely condition will be true as PT
> table is read only and  error is write_access
> and control will go to not_a_shadow_fault?
> so when the emulation code would be executed for the write that has been
> performed on read only guest PT for adding entry in
> guest page table by guest?
> Have I missed some thing here in understanding

| Yes: guest PTs are mapped with write permissions in the guest PTs. It's only
| in the shadow PTs that the guest PTs are mapped read-only. The test on
| accumulated_gflags is looking at the access permissions in the guest PTs.
| -- Keir

Does this mean that on every new entry in level 4 guest page table will cause 
recursive page faults 

to create all the entries from level 4 till level 1 shadow page table?


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