Messages in this thread | | | From | Christophe Leroy <> | Subject | Re: Regression: Linux v5.15+ does not boot on Freescale P2020 | Date | Mon, 25 Jul 2022 16:20:49 +0000 |
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Le 25/07/2022 à 14:52, Pali Rohár a écrit : > On Monday 25 July 2022 18:20:01 Michael Ellerman wrote: >> Pali Rohár <pali@kernel.org> writes: >>> On Saturday 23 July 2022 14:42:22 Christophe Leroy wrote: >>>> Le 22/07/2022 à 11:09, Pali Rohár a écrit : >>>>> Trying to boot mainline Linux kernel v5.15+, including current version >>>>> from master branch, on Freescale P2020 does not work. Kernel does not >>>>> print anything to serial console, seems that it does not work and after >>>>> timeout watchdog reset the board. >>>> >>>> Can you provide more information ? Which defconfig or .config, which >>>> version of gcc, etc ... ? >>> >>> I used default defconfig for mpc85xx with gcc 8, compilation for e500 >>> cores. >>> >>> If you need exact .config content I can send it during week. >>> >>>>> I run git bisect and it found following commit: >>>>> >>>>> 9401f4e46cf6965e23738f70e149172344a01eef is the first bad commit >>>>> commit 9401f4e46cf6965e23738f70e149172344a01eef >>>>> Author: Christophe Leroy <christophe.leroy@csgroup.eu> >>>>> Date: Tue Mar 2 08:48:11 2021 +0000 >>>>> >>>>> powerpc: Use lwarx/ldarx directly instead of PPC_LWARX/LDARX macros >>>>> >>>>> Force the eh flag at 0 on PPC32. >>>>> >>>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> >>>>> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> >>>>> Link: https://lore.kernel.org/r/1fc81f07cabebb875b963e295408cc3dd38c8d85.1614674882.git.christophe.leroy@csgroup.eu >>>>> >>>>> :040000 040000 fe6747e45736dfcba74914a9445e5f70f5120600 96358d08b65d3200928a973efb5b969b3d45f2b0 M arch >>>>> >>>>> >>>>> If I revert this commit then kernel boots correctly. It also boots fine >>>>> if I revert this commit on top of master branch. >>>>> >>>>> Freescale P2020 has two 32-bit e500 powerpc cores. >>>>> >>>>> Any idea why above commit is causing crash of the kernel? And why it is >>>>> needed? Could eh flag set to 0 cause deadlock? >>>> >>>> Setting the eh flag to 0 is not supposed to be a change introduced by >>>> that commit. Indeed that commit is not supposed to change anything at >>>> all in the generated code. >>> >>> My understanding of that commit is that it changed eh flag parameter >>> from 1 to 0 for 32-bit powerpc, including also p2020. >> >> Can you compare the disassembly before and after and find a place where >> an instruction has changed? >> >> cheers > > Yes, of course. Here is diff between output from objdump -d vmlinux. > original version --- is from git master branch and modified version +++ > is the original version with reverted above problematic commit. > So the +++ version is the one which is working. > > --- vmlinux.master.dump 2022-07-25 14:43:45.922239496 +0200 > +++ vmlinux.revert.dump 2022-07-25 14:43:49.238259296 +0200 > @@ -1,5 +1,5 @@ > > -vmlinux.master: file format elf32-powerpc > +vmlinux.revert: file format elf32-powerpc > > > Disassembly of section .head.text: > @@ -11213,7 +11213,7 @@ c000b850: 3f a0 c1 0f lis r29,-1611 > c000b854: 81 02 00 04 lwz r8,4(r2) > c000b858: 3b fd 10 68 addi r31,r29,4200 > c000b85c: 39 40 00 01 li r10,1 > -c000b860: 7d 20 f8 29 lwarx r9,0,r31,1 > +c000b860: 7d 20 f8 28 lwarx r9,0,r31 > c000b864: 2c 09 00 00 cmpwi r9,0 > c000b868: 40 82 00 10 bne c000b878 <die+0x68> > c000b86c: 7d 40 f9 2d stwcx. r10,0,r31
That's really strange. I made a try with mpc85xx_defconfig with GCC 11 and I don't get any such difference.
Does your version of GCC has anything special ?
Can you send you exact .config ?
Thanks Christophe
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