| To: | Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] page fault handling in Xen |
| From: | jeet <jeet_sat12@xxxxxxxxxxx> |
| Date: | Mon, 5 Mar 2007 18:39:03 +0530 (IST) |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | 2007年3月05日 05:08:14 -0800 |
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Hi Keir thanks for your reply.I have some more queries In HVM when guest is executing then processor looks into shadow page table for address translation. as shadow PT contains the guest pt page readonly mapping of guest level 1 page table, on which guest OS is trying to write a address of new page. 1 this would cause second VMEXit in Xen. so would faulting address be virtual address of that Guest PT page or of the shadow PT page which guest is trying to write? jeet > 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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel __________________________________________________________ Yahoo! India Answers: Share what you know. Learn something new http://in.answers.yahoo.com/ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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