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From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/106763] Armv8.2 vmov.f16 instruction sometimes causes SIGILL
Date: Wed, 31 Aug 2022 16:35:29 +0000	[thread overview]
Message-ID: <bug-106763-4-3rPPIKIveP@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-106763-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106763

--- Comment #8 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
I spoke to our kernel experts about this and they think my hypothesis is quite
likely to be correct.  They also noted that kernel version 4.9.118 is about 200
releases out of date on the 4.9 LTS series.

But more importantly, they say that trying to run a 32-bit kernel on 64-bit Arm
v8 hardware is not recommended and that you should seriously consider switching
to a 64-bit kernel (which can still run a 32-bit userland if you need it to).

I do note that the code here:
 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/kernel/entry-armv.S#n628 
does not have an entry for CP#9, which would be needed for FP16 support as all
FP16 instructions are in that part of the encoding space.  I have no idea if
changing that would be enough.

  parent reply	other threads:[~2022-08-31 16:35 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-28 14:07 [Bug target/106763] New: " georgepee at gmail dot com
2022-08-28 14:23 ` [Bug target/106763] " georgepee at gmail dot com
2022-08-28 16:15 ` georgepee at gmail dot com
2022-08-30 13:39 ` rearnsha at gcc dot gnu.org
2022-08-30 14:12 ` georgepee at gmail dot com
2022-08-30 14:16 ` rearnsha at gcc dot gnu.org
2022-08-30 14:41 ` georgepee at gmail dot com
2022-08-30 21:11 ` georgepee at gmail dot com
2022-08-31 16:35 ` rearnsha at gcc dot gnu.org [this message]
2022-09-01  0:33 ` georgepee at gmail dot com
2022-09-01  9:46 ` rearnsha at gcc dot gnu.org
2022-09-01  9:57 ` rearnsha at gcc dot gnu.org
2022-09-01 13:22 ` georgepee at gmail dot com
2022-09-01 14:32 ` rearnsha at gcc dot gnu.org
2022-09-01 14:35 ` rearnsha at gcc dot gnu.org
2022-09-01 14:54 ` georgepee at gmail dot com
2022-09-01 14:58 ` rearnsha at gcc dot gnu.org
2022-09-01 15:06 ` georgepee at gmail dot com
2022-09-01 15:14 ` rearnsha at gcc dot gnu.org

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