Hi Shrikanth, On 12/11/26 6:39 PM, Shrikanth Hegde wrote:
Christian reported that booting preemptible kernel on FSL Cyrus+ board causes boot hang.The logs pointed that system was busy in printing below warning. WARNING: at .enable_kernel_fp+0x30/0x78, CPU#3: qemu-system-ppc/4884 Modules linked in: CPU: 3 UID: 1000 PID: 4884 Comm: qemu-system-ppc Not tainted 7.3.0-rc1-powerpc64-smp-preempt #1 PREEMPT NIP [c000000000003338] .enable_kernel_fp+0x30/0x78 LR [c00000000005de84] .kvmppc_load_guest_fp+0x30/0x80 Call Trace: [c000000085ca7700] [c00000000005de84] .kvmppc_load_guest_fp+0x30/0x80 [c000000085ca7780] [c00000000005f2a0] .kvmppc_handle_exit+0x5bc/0x5cc [c000000085ca7830] [c00000000006204c] .kvmppc_resume_host+0xb8/0x10c Which is... void enable_kernel_fp(void) { unsigned long cpumsr; WARN_ON(preemptible()); And... Though irq's are hard disabled after kvmppc_prepare_to_enter, but kvmppc_fix_ee_before_entry enables the softmask's IRQ state. That causes the irqs_disabled to return false. Hence leading to the warnings. Fix it by re-ordering the code to load the FP and Altivec before enabling the softmask IRQ state. Suggested-by: Narayana Murty N <[email protected]> Fixes: 3efc7da61f6c ("KVM: PPC: Book3E: Increase FPU laziness") Reported-by: Christian Zigotzky <[email protected]> Closes: https://lore.kernel.org/all/[email protected]/ Tested-by: Christian Zigotzky <[email protected]> Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <[email protected]> Signed-off-by: Shrikanth Hegde <[email protected]> --- arch/powerpc/kvm/booke.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index 13ad4cf5fa71..aed7b476b7eb 100644 --- a/arch/powerpc/kvm/booke.c +++ b/arch/powerpc/kvm/booke.c @@ -1404,10 +1404,9 @@ int kvmppc_handle_exit(struct kvm_vcpu *vcpu, unsigned int exit_nr) if (s <= 0) r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV); else { - /* interrupts now hard-disabled */ - kvmppc_fix_ee_before_entry(); kvmppc_load_guest_fp(vcpu); kvmppc_load_guest_altivec(vcpu); + kvmppc_fix_ee_before_entry(); } }
This address my previous comment, feel free to add Reviewed-by Narayana Murty N <[email protected]>
thanks, Narayana.
