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Message-ID: <daaad0c4-75af-4b02-20d0-b0b8e327f94a@roeck-us.net> Date: Tue, 19 Sep 2017 20:45:27 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Michael Ellerman <mpe@...erman.id.au>, Christophe Leroy <christophe.leroy@....fr> Cc: linux-kernel@...r.kernel.org, Benjamin Herrenschmidt <benh@...nel.crashing.org>, linuxppc-dev@...ts.ozlabs.org, Paul Mackerras <paulus@...ba.org> Subject: Re: Traceback due to 'powerpc/mm: Fix kernel RAM protection...' when running ppc image in qemu On 09/19/2017 08:05 PM, Michael Ellerman wrote: > Guenter Roeck <linux@...ck-us.net> writes: > >> Hi, >> >> I see a the following traceback when running an SMP image based on >> 85xx/mpc85xx_cds_defconfig in qemu. >> >> ------------[ cut here ]------------ >> WARNING: CPU: 0 PID: 1 at kernel/smp.c:416 smp_call_function_many+0xcc/0x2fc >> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-rc1-00009-g0666f56 #1 >> task: cf830000 task.stack: cf82e000 >> NIP: c00a93c8 LR: c00a9634 CTR: 00000001 >> REGS: cf82fde0 TRAP: 0700 Not tainted (4.14.0-rc1-00009-g0666f56) >> MSR: 00021000 <CE,ME> CR: 24000082 XER: 00000000 >> >> GPR00: c00a9634 cf82fe90 cf830000 c050ad3c c0015a54 00000000 00000001 00000001 >> GPR08: 00000001 00000000 00000000 cf82e000 24000084 00000000 c0003150 00000000 >> GPR16: 00000000 00000000 00000000 00000000 00000000 00000001 00000000 c0510000 >> GPR24: 00000000 c0015a54 00000000 c050ad3c c051823c c050ad3c 00000025 00000000 >> NIP [c00a93c8] smp_call_function_many+0xcc/0x2fc >> LR [c00a9634] smp_call_function+0x3c/0x50 >> Call Trace: >> [cf82fe90] [00000010] 0x10 (unreliable) >> [cf82fed0] [c00a9634] smp_call_function+0x3c/0x50 >> [cf82fee0] [c0015d2c] flush_tlb_kernel_range+0x20/0x38 >> [cf82fef0] [c001524c] mark_initmem_nx+0x154/0x16c >> [cf82ff20] [c001484c] free_initmem+0x20/0x4c >> [cf82ff30] [c000316c] kernel_init+0x1c/0x108 >> [cf82ff40] [c000f3a8] ret_from_kernel_thread+0x5c/0x64 >> Instruction dump: >> 7c0803a6 7d808120 38210040 4e800020 3d20c052 812981a0 2f890000 40beffac >> 3d20c051 8929ac64 2f890000 40beff9c <0fe00000> 4bffff94 7fc3f378 7f64db78 >> ---[ end trace 7da7bdcf8b15ddb3 ]--- > > Thanks. > > I guess the system still runs OK otherwise, you're just seeing the warning? > Yes, though I am not sure if that is because there is only one active CPU (there is still only one if I say "-smp 4" on the qemu command line). >> A complete log is available at: >> http://kerneltests.org/builders/qemu-ppc-master/builds/814/steps/qemubuildcommand/logs/stdio >> >> Bisect points to commit 3184cc4b6f6a1dc0 ("powerpc/mm: Fix kernel RAM protection >> after freeing unused memory on PPC32"). Bisect log is attached. A quick look >> suggests that mark_initmem_nx() is called with interrupts disabled, which >> triggers the traceback. > > Hmm. Yes the MSR says you have interrupts disabled (EE missing). > > But I don't see why. start_kernel() did local_irq_enable(), so I don't > understand why we got to mark_initmem_nx() with them disabled. I'll hope > that Christophe has some idea. > Good question. I only see this with one of 9 ppc emulations, with 85xx/mpc85xx_cds_defconfig +CONFIG_DEVTMPFS=y +CONFIG_SMP=y. Maybe there is a platform specific init function which leaves interrupts disabled. Question is which one that might be. Guenter
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