v6.13-rc1: Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP

[Marc Zyngier]

On Mon, 02 Dec 2024 15:36:19 +0000,
Will Deacon <will at kernel.org> wrote:
> 
> [+ usual suspects]
> 
> On Mon, Dec 02, 2024 at 07:58:30AM +0300, Vitaly Chikunov wrote:
> > v6.13-rc1 exhibits a boot failure on aarch64 under KVM. (QEMU 9.1.1, CPU
> > Kunpeng-920). Boot log:
> 
> I've not tried to repro this locally, but from the log:
> 
> > + time qemu-system-aarch64 -M accel=kvm:tcg -smp cores=8 -m 4096 -serial mon:stdio -nodefaults -nographic -no-reboot -fsdev local,id=root,path=/,security_model=none,multidevs=remap -device virtio-9p-pci,fsdev=root,mount_tag=virtio-9p:/ -device virtio-rng-pci -kernel /usr/src/tmp/kernel-image-6.13-buildroot/boot/vmlinuz-6.13.0-6.13-alt0.rc1 -initrd /usr/src/tmp/initramfs-6.13.0-6.13-alt0.rc1.img -sandbox on,spawn=deny -M virt,gic-version=3 -cpu max -append 'console=ttyAMA0 mitigations=off nokaslr  panic=-1 SCRIPT=/usr/src/tmp/vm.SchsIm2FjB earlycon earlyprintk=serial ignore_loglevel debug rddebug'
> > [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x481fd010]
> > [    0.000000] Linux version 6.13.0-6.13-alt0.rc1 (builder at localhost.localdomain) (gcc-14 (GCC) 14.2.1 20241028 (ALT Sisyphus 14.2.1-alt1), GNU ld (GNU Binutils) 2.43.1.20241025) #1 SMP PREEMPT_DYNAMIC Mon Dec  2 03:33:29 UTC 2024
> > [    0.000000] KASLR disabled on command line
> > [    0.000000] random: crng init done
> > [    0.000000] Machine model: linux,dummy-virt
> > [    0.000000] printk: debug: ignoring loglevel setting.
> > [    0.000000] efi: UEFI not found.
> > [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
> > [    0.000000] printk: legacy bootconsole [pl11] enabled
> > [    0.000000] OF: reserved mem: Reserved memory: No reserved-memory node in the DT
> > [    0.000000] NUMA: Faking a node at [mem 0x0000000040000000-0x000000013fffffff]
> > [    0.000000] NODE_DATA(0) allocated [mem 0x13f7f3540-0x13f7f947f]
> > [    0.000000] Zone ranges:
> > [    0.000000]   DMA      [mem 0x0000000040000000-0x00000000ffffffff]
> > [    0.000000]   DMA32    empty
> > [    0.000000]   Normal   [mem 0x0000000100000000-0x000000013fffffff]
> > [    0.000000] Movable zone start for each node
> > [    0.000000] Early memory node ranges
> > [    0.000000]   node   0: [mem 0x0000000040000000-0x000000013fffffff]
> > [    0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x000000013fffffff]
> > [    0.000000] cma: Reserved 256 MiB at 0x00000000f0000000 on node -1
> > [    0.000000] psci: probing for conduit method from DT.
> > [    0.000000] psci: PSCIv1.1 detected in firmware.
> > [    0.000000] psci: Using standard PSCI v0.2 function IDs
> > [    0.000000] psci: Trusted OS migration not required
> > [    0.000000] psci: SMC Calling Convention v1.1
> > [    0.000000] smccc: KVM: hypervisor services detected (0x00000000 0x00000000 0x00000000 0x00000003)
> > [    0.000000] percpu: Embedded 34 pages/cpu s100632 r8192 d30440 u139264
> > [    0.000000] pcpu-alloc: s100632 r8192 d30440 u139264 alloc=34*4096
> > [    0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 [0] 4 [0] 5 [0] 6 [0] 7
> > [    0.000000] Internal error: Oops - Undefined instruction: 0000000002000000 [#1] SMP
> 
> We take an undefined instruction exception in the kernel early during
> boot...
> 
> > [    0.000000] Modules linked in:
> > [    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.13.0-6.13-alt0.rc1 #1
> > [    0.000000] Hardware name: linux,dummy-virt (DT)
> > [    0.000000] pstate: 004000c5 (nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [    0.000000] pc : __cpuinfo_store_cpu+0xe8/0x240
> > [    0.000000] lr : cpuinfo_store_boot_cpu+0x34/0x88
> > [    0.000000] sp : ffff800082013df0
> > [    0.000000] x29: ffff800082013df0 x28: 000000000000008e x27: ffff800081e38128
> > [    0.000000] x26: ffff800081702190 x25: ffff80008201f040 x24: ffff0000ff7d1d00
> > [    0.000000] x23: ffff80008201ec00 x22: ffff800081e39100 x21: ffff8000816f9750
> > [    0.000000] x20: ffff800081f55280 x19: ffff0000ff6be2e0 x18: 0000000000000000
> > [    0.000000] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> > [    0.000000] x14: 000000000000002f x13: 000000013f7f9490 x12: 0000008000000000
> > [    0.000000] x11: 0000000000000000 x10: 00000000007f8000 x9 : 000000013f808000
> > [    0.000000] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 000000013f7f94c0
> > [    0.000000] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 1100010011111111
> > [    0.000000] x2 : 0000000000000001 x1 : 0000000084448004 x0 : ffff0000ff6be2e0
> > [    0.000000] Call trace:
> > [    0.000000]  __cpuinfo_store_cpu+0xe8/0x240 (P)
> > [    0.000000]  cpuinfo_store_boot_cpu+0x34/0x88 (L)
> > [    0.000000]  cpuinfo_store_boot_cpu+0x34/0x88
> > [    0.000000]  smp_prepare_boot_cpu+0x30/0x58
> > [    0.000000]  start_kernel+0x514/0x9d0
> > [    0.000000]  __primary_switched+0x88/0x98
> > [    0.000000] Code: f100085f 54000600 f2580c7f 54000060 (d538a482)
> 
> ... and that's:
> 
>    0:	f100085f 	cmp	x2, #0x2
>    4:	54000600 	b.eq	0xc4  // b.none
>    8:	f2580c7f 	tst	x3, #0xf0000000000
>    c:	54000060 	b.eq	0x18  // b.none
>   10:*	d538a482 	mrs	x2, s3_0_c10_c4_4		<-- trapping instruction
> 
> Which I think corresponds to a read of MPAMIDR_EL1.
> 
> It looks like James routed accesses to this register to undef_access()
> in 31ff96c38ea3 ("KVM: arm64: Fix missing traps of guest accesses to the
> MPAM register") so I'm not really sure how this is supposed to work
> given that it's an ID register.

It's not. Or rather, it is an IDREG that is only valid when MPAM is
advertised and implemented. From the spec:

"This register is present only when FEAT_MPAM is implemented.
Otherwise, direct accesses to MPAMIDR_EL1 are UNDEFINED."

So from a KVM perspective, I think this is doing the right thing.

What the log doesn't say is what the host is. Is it 6.13-rc1 as well?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.