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SubjectRe: [GIT PULL] arm64: fixes for -rc6
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On 12/04/17 10:14, Will Deacon wrote:
> Hi Jon,
>
> On Tue, Apr 11, 2017 at 03:12:57PM -0400, Jon Masters wrote:
>> On 04/07/2017 12:02 PM, Will Deacon wrote:
>>
>>> Please pull these two arm64 fixes for -rc6. We've got a regression fix for
>>> the signal raised when userspace makes an unsupported unaligned access and a
>>> revert of the contiguous (hugepte) support for hugetlb, which has once again
>>> been found to be broken. One day, maybe, we'll get it right.
>>
>> <snip>
>>
>>> - Revert broken support for the contiguous bit in hugetlb (again...)
>>
>> Quick aside: is this being worked on for 4.12? If not, should we ping
>> Linaro and look to get some focus on this? It's right to disable this,
>> but also painful to those wanting to work on various NFV use cases.
>
> I think Punit and Steve (CC'd) are working on this, but the issues run
> beyond the lack of break-before-make. The core GUP code, for example,
> doesn't even support hugeptes. There are also dormant issues with hugeptes
> and swap/migration entries, which would hit if somebody flipped
> CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION. Hell, even the pte_huge macro is
> bogus if you're using contiguous ptes (granted, it's seldom used, but if
> the above are fixed maybe it will be).

Steve has a fix for the break-before-make[0].

I've posted some fixes for contiguous hugepages support in preparation
for enabling memory failure handling[1] but as the changes touch
multiple architectures, it may take some time to merge.

I'll take a look at the GUP code next but no promises on a timeframe yet.

Thanks,
Punit

[0]
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-March/497027.html
[1] https://lwn.net/Articles/718974/
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