RE: [Xen-devel] Regarding page table management changes from Xen v1to Xen v2 (and v3)

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> In another example, mmapped access to a file, the new 
> approach will incur these two extra faults for every page 
> fault required to bring a file page to page cache, right?

No, these singleton updates on the Linux demand fault path are issued
with the update_va_mapping hypercall. This is possible because the
virtual address that the pte maps is known, so its possible for Xen to
use a linear pagetable to do the update rather than creating an
on-demand mapping to the domain's pagetable page. This is an important
optimization on 32b where Xen address space is tight.

Ian

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