Re: Illegal operation with clang + CONFIG_MARCH_Z13

[Nathan Chancellor <nathan@kernel.org>]

On Wed, Sep 14, 2022 at 11:50:52AM +0200, Christian Borntraeger wrote:
> Am 14.09.22 um 11:00 schrieb Nathan Chancellor:
> > On Wed, Sep 14, 2022 at 08:03:47AM +0200, Christian Borntraeger wrote:
> > > Am 13.09.22 um 19:34 schrieb Nathan Chancellor:
> > > > Hi all,
> > > > 
> > > > Recently, Fedora moved their baseline from CONFIG_MARCH_ZEC12 to
> > > > CONFIG_MARCH_Z13:
> > > > 
> > > > https://src.fedoraproject.org/rpms/kernel/c/aff6e8acdaa437e9f06ef4166ca2209071223f8d
> > > > 
> > > > Unfortunately, this causes clang built kernels to have an "illegal
> > > > operation" panic when booting in QEMU. This is trivially reproducible on
> > > > mainline with the versions of clang that s390 supports.
> > > > 
> > > > # Switch from CONFIG_MARCH_ZEC12 to CONFIG_MARCH_Z13
> > > > $ make -skj"$(nproc)" ARCH=s390 CC=clang CROSS_COMPILE=s390x-linux-gnu- defconfig menuconfig bzImage
> > > > 
> > > > $ qemu-system-s390x \
> > > > -M s390-ccw-virtio \
> > > > -kernel arch/s390/boot/bzImage \
> > > > -display none \
> > > > -initrd .../boot-utils/images/s390/rootfs.cpio \
> > > > -m 512m \
> > > > -nodefaults \
> > > > -no-reboot \
> > > > -serial mon:stdio
> > > > ...
> > > > [    0.558817] Linux version 6.0.0-rc5-00017-gd1221cea11fc (nathan@distrobox-oTN5YGrt3J.thelio-3990X) (clang version 14.0.5 (Fedora 14.0.5-7.fc38), GNU ld version 2.38-4.fc37) #1 SMP Tue Sep 13 08:35:38 MST 2022
> > > > ...
> > > > [    1.675787] illegal operation: 0001 ilc:3 [#1] SMP
> > > > [    1.675888] Modules linked in:
> > > > [    1.676044] CPU: 0 PID: 59 Comm: modprobe Not tainted 6.0.0-rc5-00017-gd1221cea11fc #1
> > > > [    1.676134] Hardware name: QEMU 8561 QEMU (KVM/Linux)
> > > 
> > > What qemu version is that and what command line did you use (any cpu model?)
> > 
> > I was able to reproduce this with QEMU 6.0.0 through 7.1.0, which are
> > the versions that can boot a clang built kernel. I don't think we
> > specify a cpu model, you can see the full command above. If there is
> > something we should be doing differently, please let us know!
> > 
> > > > [    1.676202] Krnl PSW : 0704d00180000000 0000000000579fbc (load_elf_binary+0x31c/0x11c0)
> > > > [    1.676459]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
> > > > [    1.676489] Krnl GPRS: 0000000000000001 00000000044f0000 0000000000000000 0000000000000000
> > > > [    1.676506]            8000000000000080 0000000000000000 0000000000000000 00000000035fa900
> > > > [    1.676522]            0000000000000001 000000000353ce00 0000000000000001 00000000044693c0
> > > > [    1.676538]            000000000276fa00 000000000446a000 0000000000579f9e 00000380002ebc78
> > > > [    1.677128] Krnl Code: 0000000000579fac: a7f405b8            brc     15,000000000057ab1c
> > > > [    1.677128]            0000000000579fb0: e31003400004        lg      %r1,832
> > > > [    1.677128]           #0000000000579fb6: e3001780003b        lzrf    %r0,1920(%r1)
> > > 
> > > QEMU does support lzrf as far asI can tell as soon as you have S390_FEAT_STFLE_53 which is part
> > > of the qemu_V4_1 cpu model.
> > > 
> > > > [    1.677128]           >0000000000579fbc: 50001780            st      %r0,1920(%r1)
> > > > [    1.677128]            0000000000579fc0: e31003400004        lg      %r1,832
> > > > [    1.677128]            0000000000579fc6: c40800aa99a9        lgrl    %r0,0000000001acd318
> > > > [    1.677128]            0000000000579fcc: e3001d400124        stg     %r0,7488(%r1)
> > > > [    1.677128]            0000000000579fd2: e31003400004        lg      %r1,832
> 
> 
> Can you check if the following qemu patch helps?

Yes, that appears to work for me! If you send it along formally, feel
free to include:

Tested-by: Nathan Chancellor <nathan@kernel.org>

> diff --git a/target/s390x/tcg/insn-data.def b/target/s390x/tcg/insn-data.def
> index 5e448bb2c488..6bb479340a38 100644
> --- a/target/s390x/tcg/insn-data.def
> +++ b/target/s390x/tcg/insn-data.def
> @@ -466,7 +466,7 @@
>      C(0xe39f, LAT,     RXY_a, LAT, 0, m2_32u, r1, 0, lat, 0)
>      C(0xe385, LGAT,    RXY_a, LAT, 0, a2, r1, 0, lgat, 0)
>  /* LOAD AND ZERO RIGHTMOST BYTE */
> -    C(0xe3eb, LZRF,    RXY_a, LZRB, 0, m2_32u, new, r1_32, lzrb, 0)
> +    C(0xe33b, LZRF,    RXY_a, LZRB, 0, m2_32u, new, r1_32, lzrb, 0)
>      C(0xe32a, LZRG,    RXY_a, LZRB, 0, m2_64, r1, 0, lzrb, 0)
>  /* LOAD LOGICAL AND ZERO RIGHTMOST BYTE */
>      C(0xe33a, LLZRGF,  RXY_a, LZRB, 0, m2_32u, r1, 0, lzrb, 0)
>