[PATCH][Xenial] UBUNTU: [Config] CONFIG_ARM64_VA_BITS=48

Tim Gardner tim.gardner at canonical.com
Tue Feb 2 13:04:16 UTC 2016


On 02/02/2016 05:30 AM, Tim Gardner wrote:
> On 02/01/2016 03:31 PM, dann frazier wrote:
>> On Fri, Jan 29, 2016 at 06:23:35PM -0700, dann frazier wrote:
>>> On NUMA implementations of Cavium ThunderX, node1 memory addresses start with
>>> bit 40 set to 1, and therefore requires >= 41 bits of VA.
>>>
>>> Since we are using 4K pages, this also means moving from 3 to 4 level page
>>> tables. The alternative would be increasing our page size. Upstream supports
>>> 16K and 64K pages; 16K pages are not universally supported by ARM64 SoCs.
>>>
>>> 64K pages are pretty universal, but has issues of it's own:
>>>   https://bugs.launchpad.net/skipper/+bug/1522204
>>
>> Oops - that should be: http://bugs.launchpad.net/bugs/1520162
>>
> 
> That bug makes it sound like we might be opening a can of worms with 64K
> pages. Any thoughts on how much carnage this might cause ? Maybe we
> should wait until binutils has been adjusted so that 4K applications are
> 64K aligned ?
> 
> rtg
> 

Never mind. Paolo explained to me what this patch actually does. Could
you add an annotation in debian.master/config/annotations so that we
remember why we've made this change ?

rtg

-- 
Tim Gardner tim.gardner at canonical.com




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