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Bug#771997: marked as done (swp on armv8 (Was: Haskell on arm needs help))

Your message dated Tue, 11 Jun 2019 15:04:21 +0200
with message-id <20190611130421.GA6530@pisco.westfalen.local>
and subject line Re: swp on armv8 (Was: Haskell on arm needs help)
has caused the Debian Bug report #771997,
regarding swp on armv8 (Was: Haskell on arm needs help)
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
771997: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=771997
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Source: linux
Version: 3.16.7-2
Severity: important
X-Debbugs-CC: debian-arm@lists.debian.org

On Thu, 2014-12-04 at 08:38 +0000, Ian Campbell wrote:
> On Wed, 2014-12-03 at 23:23 +0000, peter green wrote:
> 
> > I vaugely remember something a while back about some deprecated 32-bit 
> > arm instructions needing kernel emulation on armv8 and that emulation 
> > not being implemented yet.
> 
> That's correct, and IIRC swp is one of those instructions.
> 
> > AIUI swp is already handled through kernel emulation on armv7 
> > multiprocessor systems. There seem to be patches to port that emulation 
> > to arm64 but it doesn't appear they are in the kernel tree debian is 
> > using.
> >  Having 32-bit binaries break on armv8 systems due to lack of the 
> > swp instruction does not seem like a good thing so IMO we really want 
> > this in our kernels before release.
> 
> If those patches have gone into a later upstream kernel than we have in
> Jessie (v3.16) then we should certainly backport them. IIRC they were
> controversial though, so if they haven't hit mainline I'd be *very*
> reluctant to "fork" the v8 userspace ABI.

They are in the arm64 maintainer's for-next/core branch but not in
Linus' tree (yet):
        $ git log --oneline v3.16..origin/master -- arch/arm64/kernel/armv8_deprecated.c
        $ git log --oneline v3.16..arm64/for-next/core -- arch/arm64/kernel/armv8_deprecated.c
        9096339 arm64: fix return code check when changing emulation handler
        d784e29 arm64: Trace emulation of AArch32 legacy instructions
        c852f32 arm64: Emulate CP15 Barrier instructions
        bd35a4a arm64: Port SWP/SWPB emulation support from arm
        587064b arm64: Add framework for legacy instruction emulation
        
I've bcc'd submit@ on this mail to create a bug for tracking. I think
I'm happy to backport now (FSVO "now" depending on when I get a moment),
since these are clearly en route to Linus.

Note that after these patches SWP is still undef by default, this just
adds the option to emulate (via a sysctl toggle). I don't propose to
deviate from upstream here, since they have good reasons to prefer the
current defaults.

Ian.

--- End Message ---
--- Begin Message --- 
On Thu, Dec 04, 2014 at 08:52:52AM +0000, Ian Campbell wrote:
> Source: linux
> Version: 3.16.7-2
> Severity: important
> X-Debbugs-CC: debian-arm@lists.debian.org
> 
> On Thu, 2014-12-04 at 08:38 +0000, Ian Campbell wrote:
> > On Wed, 2014-12-03 at 23:23 +0000, peter green wrote:
> > 
> > > I vaugely remember something a while back about some deprecated 32-bit 
> > > arm instructions needing kernel emulation on armv8 and that emulation 
> > > not being implemented yet.
> > 
> > That's correct, and IIRC swp is one of those instructions.
> > 
> > > AIUI swp is already handled through kernel emulation on armv7 
> > > multiprocessor systems. There seem to be patches to port that emulation 
> > > to arm64 but it doesn't appear they are in the kernel tree debian is 
> > > using.
> > >  Having 32-bit binaries break on armv8 systems due to lack of the 
> > > swp instruction does not seem like a good thing so IMO we really want 
> > > this in our kernels before release.
> > 
> > If those patches have gone into a later upstream kernel than we have in
> > Jessie (v3.16) then we should certainly backport them. IIRC they were
> > controversial though, so if they haven't hit mainline I'd be *very*
> > reluctant to "fork" the v8 userspace ABI.
> 
> They are in the arm64 maintainer's for-next/core branch but not in
> Linus' tree (yet):
>         $ git log --oneline v3.16..origin/master -- arch/arm64/kernel/armv8_deprecated.c
>         $ git log --oneline v3.16..arm64/for-next/core -- arch/arm64/kernel/armv8_deprecated.c
>         9096339 arm64: fix return code check when changing emulation handler
>         d784e29 arm64: Trace emulation of AArch32 legacy instructions
>         c852f32 arm64: Emulate CP15 Barrier instructions
>         bd35a4a arm64: Port SWP/SWPB emulation support from arm
>         587064b arm64: Add framework for legacy instruction emulation
>         
> I've bcc'd submit@ on this mail to create a bug for tracking. I think
> I'm happy to backport now (FSVO "now" depending on when I get a moment),
> since these are clearly en route to Linus.

Closing, these are not going to be backported to Jessie at this point.

Cheers,
        Moritz

--- End Message ---
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