Re: [PATCH v5 00/30] ARM Scalable Vector Extension (SVE)

Yury Norov
2018-01-08T14:44:43Z

On Tue, Oct 31, 2017 at 03:50:52PM +0000, Dave Martin wrote:
> This series implements Linux kernel support for the ARM Scalable Vector
> Extension (SVE). [1] It supersedes the previous v3: see [3] for link
> and full cover letter.
>
> This is a minor update to v4, but does contain a couple of important
> fixes.
>
> As in previous postings, the last two patches (here 29-30) are still
> RFC and not proposed for merging at this time.
>
> The patches apply on
> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
> for-next/core
> d7b1d22d3821 ("arm64: uapi: Remove PSR_Q_BIT")
>
> To reduce spam, some people may not been copied on the entire series.
> For those who did not receive the whole series, it can be found in the
> linux-arm-kernel archive. [2]
>
> See the individual patches for details of changes.
>
> For reviewer convenience, a git tree is available. [4]
>
> Since there are some changes against already-reviewed patches, I've also
> pushed an unsquashed fixes tree for people to take a look at if it
> helps. [5]
>
>
> Summary:
>
> * "regset: Add support for dynamically sized regsets" fixed to avoid
> x86 breakage;
>
> * one trival arm64 patch added to add asmlinkage annotations, and a
> corresponding minor change to the Core task context handling patch;
>
> * one new arm64 fix ("signal: Verify extra data is user-readable in
> sys_rt_sigreturn") to ensure that access_ok() checks are done for the
> whole extended signal frame, not just the base frame;
>
> * one minor fix to the SVE sigreturn code to return consistent
> intermediate error values (semantic correctness, non-functional
> change);
>
> * one minor change to call __copy_from_user() instead of
> copy_from_user() in a situation where there is already an access_ok()
> check;
>
>
> [1] ARM Scalable Vector Extension
> https://community.arm.com/groups/processors/blog/2016/08/22/technology-update-the-scalable-vector-extension-sve-for-the-armv8-a-architecture
>
> [2] linux-arm-kernel October 2017 Archives by thread
> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-October/thread.html
>
> [3] [PATCH v4 00/28] ARM Scalable Vector Extension (SVE)
> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-October/539414.html
>
> [4] For review and testing only -- **do not pull**
> (This branch has review changelogs which should not form part of
> the final commits.)
>
> v5 series (this posting)
>
> http://linux-arm.org/git?p=linux-dm.git;a=shortlog;h=refs/heads/sve/v5
> git://linux-arm.org/linux-dm.git sve/v5
>
> [5] For review and testing only -- **do not pull**
> (This branch has review changelogs which should not form part of
> the final commits.)
>
> v4 with unsquashed fixes
>
> http://linux-arm.org/git?p=linux-dm.git;a=shortlog;h=refs/heads/sve/v4%2Bfixes
> git://linux-arm.org/linux-dm.git sve/v4+fixes

Hi Dave,

During rebase of my ILP32 series on 4.15 kernel I found that
ILP32 needs to be enabled with SVE support, like you do for
LP64 in this series.

I did all rebase work on this draft branch:
https://github.com/norov/linux/tree/ilp32-4.15-rc7

But any ILP32 program I tried crash, and the message in dmesg looks
like this:
[ 39.510667] CPU: 0 PID: 1857 Comm: mytime Not tainted 4.15.0-rc7-00028-g45e0659df4d9 #41
[ 39.510712] Hardware name: linux,dummy-virt (DT)
[ 39.510829] pstate: 00000000 (nzcv daif -PAN -UAO)
[ 39.511101] pc : 0x33488e28
[ 39.511125] lr : 0x33488e28
[ 39.511138] sp : 00000000fffef670
[ 39.511158] x29: 000000005a536c33 x28: 0000000000000000
[ 39.511211] x27: 0000000000000000 x26: 0000000000000000
[ 39.511235] x25: 0000000000000000 x24: 0000000000000000
[ 39.511257] x23: 0000000000466000 x22: 0000000000000000
[ 39.511278] x21: 0000000000000000 x20: 000000000047f2a8
[ 39.511300] x19: 0000000000000000 x18: 0000000000000001
[ 39.511321] x17: 0000000000001000 x16: 0000000000001030
[ 39.511342] x15: 0000000000554e47 x14: 0000000000000001
[ 39.511364] x13: 0000000000000004 x12: 000000000000003c
[ 39.511385] x11: 0000100000000000 x10: 0800000000000000
[ 39.511406] x9 : 0fffffffffffffff x8 : 000000000000007c
[ 39.511427] x7 : 0000000000000077 x6 : 0000000000000041
[ 39.511448] x5 : 0000000000000411 x4 : 00000000fbad2488
[ 39.511468] x3 : 0000000000000001 x2 : 0000000000497950
[ 39.511489] x1 : 0000000000497550 x0 : 0000000000000001

(PC, LR and other registers may differ depending on test)

I'm pretty sure that this is SVE-related issue because if I disable
ARM64_SVE in config, everything becomes working.

I didn't get deep enough into this yet, and most probably there's
some stupid reason for crashing apps on my side, but in mail list
I found some sve-related patches that I cannot apply both on 4.15-rc
and next-20180108. And according to patch names, it is important
fixes, like this one:
https://www.spinics.net/lists/arm-kernel/msg619548.html

ILP32 code may spit some kernel issues from time to time, so there's
minor chance that the problem is not in ILP32 itself - that's why I
write this email to you.

What I want to ask you, do you have some branch with the most recent
SVE code that includes all fixes? Better if it would be 4.15-based
series, because we don't support ILP32 on next-* kernels now.

Also, if you have few minutes to take look at my series, I would
kindly ask you do this, because I still think that this is my
misunderstanding of how SVE should work for ILP32, and you as author
may just catch the bug at a glance.

Thanks,
Yury