[Xen-devel] why each process needs a separate page for kernel's pgd table in PV x86_64?

[weiming <zephyr.zhao@xxxxxxxxx>]

Hi,

I notice that in the paravirtualized linux for x86_64, each process allocates 2 pages for mm->pgd: one for kernel's page table, the other for user's page table.

Why not let all processes share the kernel's page table? i.e., add a field in mm struct (like mm->kernel_pgd, ) and let it point to a page, which will be referenced by all process. This can save some 4K for each process forked.

Please correct me if I'm wrong.

Thanks,
Weiming
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