Messages in this thread | | | Subject | Re: [PATCH 1/2] KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy | From | Zenghui Yu <> | Date | Tue, 14 Apr 2020 19:17:49 +0800 |
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Hi Marc,
On 2020/4/14 18:54, Marc Zyngier wrote: > On Tue, 14 Apr 2020 11:03:47 +0800 > Zenghui Yu <yuzenghui@huawei.com> wrote: > > Hi Zenghui, > >> It's likely that the vcpu fails to handle all virtual interrupts if >> userspace decides to destroy it, leaving the pending ones stay in the >> ap_list. If the un-handled one is a LPI, its vgic_irq structure will >> be eventually leaked because of an extra refcount increment in >> vgic_queue_irq_unlock(). >> >> This was detected by kmemleak on almost every guest destroy, the >> backtrace is as follows: >> >> unreferenced object 0xffff80725aed5500 (size 128): >> comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s) >> hex dump (first 32 bytes): >> 00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm... >> c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l... >> backtrace: >> [<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418 >> [<0000000069c7dabb>] vgic_add_lpi+0x88/0x418 >> [<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588 >> [<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198 >> [<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80 >> [<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108 >> [<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188 >> [<000000008f79d288>] __kvm_io_bus_write+0x134/0x240 >> [<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150 >> [<0000000078197602>] io_mem_abort+0x484/0x7b8 >> [<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58 >> [<00000000e0d0cd65>] handle_exit+0x24c/0x770 >> [<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988 >> [<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0 >> [<000000003271e317>] do_vfs_ioctl+0x160/0xcd8 >> [<00000000e7f39607>] ksys_ioctl+0x98/0xd8 >> >> Fix it by retiring all pending LPIs in the ap_list on the destroy path. >> >> p.s. I can also reproduce it on a normal guest shutdown. It is because >> userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while >> the guest is being shutdown and unable to handle it. A little strange >> though and haven't dig further... > > What userspace are you using? You'd hope that the VMM would stop > processing I/Os when destroying the guest. But we still need to handle > it anyway, and I thing this fix makes sense.
I'm using Qemu (master) for debugging. Looks like an interrupt corresponding to a virtio device configuration change, triggered after all other devices had freed their irqs. Not sure if it's expected.
>> >> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com> >> --- >> virt/kvm/arm/vgic/vgic-init.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c >> index a963b9d766b7..53ec9b9d9bc4 100644 >> --- a/virt/kvm/arm/vgic/vgic-init.c >> +++ b/virt/kvm/arm/vgic/vgic-init.c >> @@ -348,6 +348,12 @@ void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu) >> { >> struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; >> >> + /* >> + * Retire all pending LPIs on this vcpu anyway as we're >> + * going to destroy it. >> + */ >> + vgic_flush_pending_lpis(vcpu); >> + >> INIT_LIST_HEAD(&vgic_cpu->ap_list_head); >> } >> > > I guess that at this stage, the INIT_LIST_HEAD() is superfluous, right?
I was just thinking that the ap_list_head may not be empty (besides LPI, with other active or pending interrupts), so leave it unchanged.
> Otherwise, looks good. If you agree with the above, I can fix that > locally, no need to resend this patch.
Thanks, Zenghui
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