Hi, On 04/03/2019 17:06, Marc Zyngier wrote:
On 04/03/2019 16:30, Julien Grall wrote:Hi, I noticed some issues with this patch when rebooting a guest after using perf. [ 577.513447] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:908 [ 577.521926] in_atomic(): 1, irqs_disabled(): 0, pid: 2323, name: qemu-system aar [ 577.529354] 1 lock held by qemu-system-aar/2323: [ 577.533998] #0: 00000000f4f96804 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x74/0xac0 [ 577.541865] Preemption disabled at: [ 577.541871] [<ffff0000100cc82c>] kvm_reset_vcpu+0x1c/0x1d0 [ 577.550882] CPU: 6 PID: 2323 Comm: qemu-system-aar Tainted: G W 5.0.0 #1277 [ 577.559137] Hardware name: AMD Seattle (Rev.B0) Development Board (Overdrive) (DT) [ 577.566698] Call trace: [ 577.569138] dump_backtrace+0x0/0x140 [ 577.572793] show_stack+0x14/0x20 [ 577.576103] dump_stack+0xa0/0xd4 [ 577.579412] ___might_sleep+0x1e4/0x2b0 [ 577.583241] __might_sleep+0x60/0xb8 [ 577.586810] __mutex_lock+0x58/0x860 [ 577.590378] mutex_lock_nested+0x1c/0x28 [ 577.594294] perf_event_ctx_lock_nested+0xf4/0x238 [ 577.599078] perf_event_read_value+0x24/0x60 [ 577.603341] kvm_pmu_get_counter_value+0x80/0xe8 [ 577.607950] kvm_pmu_stop_counter+0x2c/0x98 [ 577.612126] kvm_pmu_vcpu_reset+0x58/0xd0 [ 577.616128] kvm_reset_vcpu+0xec/0x1d0 [ 577.619869] kvm_arch_vcpu_ioctl+0x6b0/0x860 [ 577.624131] kvm_vcpu_ioctl+0xe0/0xac0 [ 577.627876] do_vfs_ioctl+0xbc/0x910 [ 577.631443] ksys_ioctl+0x78/0xa8 [ 577.634751] __arm64_sys_ioctl+0x1c/0x28 [ 577.638667] el0_svc_common+0x90/0x118 [ 577.642408] el0_svc_handler+0x2c/0x80 [ 577.646150] el0_svc+0x8/0xc This is happening because the vCPU reset code is now running with preemption disable. However, the perf code cannot be called with preemption disabled as it is using mutex. Do you have any suggestion on the way to fix this potential issue?Given that the PMU is entirely emulated, it never has any state loaded on the CPU. It thus doesn't need to be part of the non-preemptible section. Can you please give this (untested) patchlet one a go? It's not exactly pretty, but I believe it will do the trick.
It does the trick. Are you going to submit the patch? Cheers, -- Julien Grall _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
