Messages in this thread | | | Date | Tue, 28 Oct 2014 06:00:20 +0100 | From | Juergen Gross <> | Subject | Re: [PATCH 0/2] xen: Switch to virtual mapped linear p2m list |
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On 10/27/2014 04:16 PM, David Vrabel wrote: > On 27/10/14 14:52, Juergen Gross wrote: >> Paravirtualized kernels running on Xen use a three level tree for >> translation of guest specific physical addresses to machine global >> addresses. This p2m tree is used for construction of page table >> entries, so the p2m tree walk is performance critical. >> >> By using a linear virtual mapped p2m list accesses to p2m elements >> can be sped up while even simplifying code. To achieve this goal >> some p2m related initializations have to be performed later in the >> boot process, as the final p2m list can be set up only after basic >> memory management functions are available. > > What impact does this have on 32-bit guests which don't have huge amount > of virtual address space? > > I think a 32-bit guest could have up to 64 GiB of PFNs, which would > require a 128 MiB p2m array, which is too large?
It is 64 MB (one entry on 32 bit is 32 bits :-) ).
With a m2p array of only 16 MB size I doubt a 32 bit guest can be larger than 16 GB, or am I wrong here?
Juergen
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