Benjamin LaHaise wrote:
> Are you switching mms in order to avoid all of the overhead associated with
> flushing an active mm during task exit? If so, it makes much more sense to
> do this in the generic helper, as it should be a win on x86 and x86-64
> where switching to init_mm is relatively low cost given the support for
> global pages. I'll run some tests on a couple of systems this evening and
> post the results.
Under Xen, the pagetables are mapped read-only to the guest, so all
pagetable updates need to go via the hypervisor. If we switch to
init_mm and unpin (make all the pages RW) before pulling the pagetable
apart, then we can just traverse and modify the pagetable memory as
normal RW memory. It avoids a heap of traps into the hypervisor.
J
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