Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH v2] Call xen_cleanhighmap() with 4MB aligned for page tables mapping | From | Andrew Cooper <> | Date | Wed, 27 Sep 2017 16:03:37 +0100 |
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On 27/09/17 15:56, Juergen Gross wrote: > On 27/09/17 16:48, Boris Ostrovsky wrote: >> On 09/27/2017 10:33 AM, Juergen Gross wrote: >>> On 27/09/17 15:38, Boris Ostrovsky wrote: >>>> On 09/27/2017 05:43 AM, Juergen Gross wrote: >>>>> On 27/09/17 11:41, Zhenzhong Duan wrote: >>>>>> When bootup a PVM guest with large memory(Ex.240GB), XEN provided initial >>>>>> mapping overlaps with kernel module virtual space. When mapping in this space >>>>>> is cleared by xen_cleanhighmap(), in certain case there could be an 2MB mapping >>>>>> left. This is due to XEN initialize 4MB aligned mapping but xen_cleanhighmap() >>>>>> finish at 2MB boundary. >>>> Does this mapping need to be 4MB-aligned? >>> I guess you are questioning the alignment of addr to be 4MB? >>> In this case you are right: the end of the mapping is 4MB aligned, as >>> correctly stated in the comment added. >> Yes, and my question is why does it need to be aligned on 4MB. Doesn't >> 2MB alignment suffice? > I believe this has historical reasons. :-)
Back in the day, superpages had 4M alignment.
~Andrew
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