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Re: [GIT PULL] arm64: fixes for -rc6

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  Re: [GIT PULL] arm64: fixes for -rc6 Jon Masters <jcm@redhat.com> - 2017-04-11 21:20 +0200
    Re: [GIT PULL] arm64: fixes for -rc6 Will Deacon <will.deacon@arm.com> - 2017-04-12 11:20 +0200

#1621572 — Re: [GIT PULL] arm64: fixes for -rc6

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.

Jon.

-- 
Computer Architect | Sent from my Fedora powered laptop

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#1621951

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).

Will

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