On Fri, 2019-10-04 at 02:53:17 UTC, Jordan Niethe wrote:
> kvmhv_switch_to_host() in arch/powerpc/kvm/book3s_hv_rmhandlers.S needs
> to set kvmppc_vcore->in_guest to 0 to signal secondary CPUs to continue.
> This happens after resetting the PCR. Before commit 13c7bb3c57dc
> ("powerpc/64s: Set reserved PCR bits"), r0 would always be 0 before it
> was stored to kvmppc_vcore->in_guest. However because of this change in
> the commit:
>
> /* Reset PCR */
> ld r0, VCORE_PCR(r5)
> - cmpdi r0, 0
> + LOAD_REG_IMMEDIATE(r6, PCR_MASK)
> + cmpld r0, r6
> beq 18f
> - li r0, 0
> - mtspr SPRN_PCR, r0
> + mtspr SPRN_PCR, r6
> 18:
> /* Signal secondary CPUs to continue */
> stb r0,VCORE_IN_GUEST(r5)
>
> We are no longer comparing r0 against 0 and loading it with 0 if it
> contains something else. Hence when we store r0 to
> kvmppc_vcore->in_guest, it might not be 0. This means that secondary
> CPUs will not be signalled to continue. Those CPUs get stuck and errors
> like the following are logged:
>
> KVM: CPU 1 seems to be stuck
> KVM: CPU 2 seems to be stuck
> KVM: CPU 3 seems to be stuck
> KVM: CPU 4 seems to be stuck
> KVM: CPU 5 seems to be stuck
> KVM: CPU 6 seems to be stuck
> KVM: CPU 7 seems to be stuck
>
> This can be reproduced with:
> $ for i in `seq 1 7` ; do chcpu -d $i ; done ;
> $ taskset -c 0 qemu-system-ppc64 -smp 8,threads=8 \
> -M pseries,accel=kvm,kvm-type=HV -m 1G -nographic -vga none \
> -kernel vmlinux -initrd initrd.cpio.xz
>
> Fix by making sure r0 is 0 before storing it to kvmppc_vcore->in_guest.
>
> Fixes: 13c7bb3c57dc ("powerpc/64s: Set reserved PCR bits")
> Reported-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> Signed-off-by: Jordan Niethe <jniethe5@xxxxxxxxx>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/7fe4e1176dfe47a243d8edd98d26abd11f91b042
cheers
