Re: [PATCH v3 29/32] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts

Shaokun Zhang
2020-01-15T02:49:43Z

Hi Marc, [This is from Nianyao]

On 2019/12/24 19:10, Marc Zyngier wrote:
> In order to let a guest buy in the new, active-less SGIs, we
> need to be able to switch between the two modes.
>
> Handle this by stopping all guest activity, transfer the state
> from one mode to the other, and resume the guest.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> include/kvm/arm_vgic.h | 3 ++
> virt/kvm/arm/vgic/vgic-v3.c | 2 +
> virt/kvm/arm/vgic/vgic-v4.c | 96 +++++++++++++++++++++++++++++++++++++
> virt/kvm/arm/vgic/vgic.h | 1 +
> 4 files changed, 102 insertions(+)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 63457908c9c4..69f4164d6477 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -231,6 +231,9 @@ struct vgic_dist {
> /* distributor enabled */
> bool enabled;
>
> + /* Wants SGIs without active state */
> + bool nassgireq;
> +
> struct vgic_irq *spis;
>
> struct vgic_io_device dist_iodev;
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index c2fdea201747..c79a251c4974 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm)
> goto out;
> }
>
> + if (kvm_vgic_global_state.has_gicv4_1)
> + vgic_v4_configure_vsgis(kvm);
> dist->ready = true;
>
> out:
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index c2fcde104ea2..063785fd2dc7 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -97,6 +97,102 @@ static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
> return IRQ_HANDLED;
> }
>
> +static void vgic_v4_sync_sgi_config(struct its_vpe *vpe, struct vgic_irq *irq)
> +{
> + vpe->sgi_config[irq->intid].enabled = irq->enabled;
> + vpe->sgi_config[irq->intid].group = irq->group;
> + vpe->sgi_config[irq->intid].priority = irq->priority;
> +}
> +
> +static void vgic_v4_enable_vsgis(struct kvm_vcpu *vcpu)
> +{
> + struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
> + int i;
> +
> + /*
> + * With GICv4.1, every virtual SGI can be directly injected. So
> + * let's pretend that they are HW interrupts, tied to a host
> + * IRQ. The SGI code will do its magic.
> + */
> + for (i = 0; i < VGIC_NR_SGIS; i++) {
> + struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
> + struct irq_desc *desc;
> + int ret;
> +
> + if (irq->hw) {
> + vgic_put_irq(vcpu->kvm, irq);
> + continue;
> + }
> +
> + irq->hw = true;
> + irq->host_irq = irq_find_mapping(vpe->sgi_domain, i);

I think we need to check whether irq_find_mapping returns 0.

> + vgic_v4_sync_sgi_config(vpe, irq);
> + /*
> + * SGIs are initialised as disabled. Enable them if
> + * required by the rest of the VGIC init code.
> + */
> + desc = irq_to_desc(irq->host_irq);
> + ret = irq_domain_activate_irq(irq_desc_get_irq_data(desc),
> + false);

If irq->host_irq is not valid , in irq_domain_activate_irq, it will trigger NULL pointer
dereference in host kernel.
I meet a problem here. When hw support GIC4.1, and host kernel is started with
kvm-arm.vgic_v4_enable=0, starting a virtual machine will trigger NULL pointer
dereference in host. The following is error info:

[ 7.913815] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038
[ 7.913818] Mem abort info:
[ 7.913819] ESR = 0x96000007
[ 7.913821] EC = 0x25: DABT (current EL), IL = 32 bits
[ 7.913823] SET = 0, FnV = 0
[ 7.913825] EA = 0, S1PTW = 0
[ 7.913827] Data abort info:
[ 7.913828] ISV = 0, ISS = 0x00000007
[ 7.913830] CM = 0, WnR = 0
[ 7.913832] user pgtable: 64k pages, 48-bit VAs, pgdp=00000824405a0800
[ 7.913835] [0000000000000038] pgd=0000082444120003, pud=0000082444120003, pmd=0000082444130003, pte=0000000000000000
[ 7.913840] Internal error: Oops: 96000007 [#1] SMP
[ 7.913842] Modules linked in:
[ 7.913845] CPU: 1 PID: 1918 Comm: qemu-system-aar Tainted: G W 5.5.0-rc2-14819-g4e11d8f-dirty #20
[ 7.913849] pstate: 80400009 (Nzcv daif +PAN -UAO)
[ 7.913852] pc : irq_domain_activate_irq+0x0/0x58
[ 7.913854] lr : vgic_v4_configure_vsgis+0x108/0x208
[ 7.913857] sp : ffff8000160af7b0
[ 7.913858] x29: ffff8000160af7b0 x28: ffff082445030000
[ 7.913861] x27: 0000000000000004 x26: ffff0824456032c8
[ 7.913864] x25: 0000000000000000 x24: ffff8000118d1130
[ 7.913868] x23: 0000000000000001 x22: ffff8000118d0000
[ 7.913871] x21: 0000000000000000 x20: ffff082445602360
[ 7.913874] x19: ffff082445603348 x18: 0000000000000010
[ 7.913877] x17: 0000000000000050 x16: 0000000000000001
[ 7.913880] x15: ffff8000110eb258 x14: ffffffffffffffff
[ 7.913883] x13: ffff8000910cfb17 x12: ffff8000110cfb24
[ 7.913886] x11: ffff8000110f8000 x10: 0000000000000040
[ 7.913889] x9 : ffff8000110f8fe0 x8 : ffff8000110f8fd8
[ 7.913892] x7 : ffff082420000270 x6 : 0000000000000000
[ 7.913895] x5 : ffff082420000248 x4 : 0000000000000000
[ 7.913898] x3 : 0000000000000000 x2 : 0000000000000000
[ 7.913901] x1 : 0000000000000000 x0 : 0000000000000028
[ 7.913904] Call trace:
[ 7.913907] irq_domain_activate_irq+0x0/0x58
[ 7.913909] vgic_mmio_write_v3_misc+0xf0/0x100
[ 7.913912] dispatch_mmio_write+0x78/0x100
[ 7.913915] __kvm_io_bus_write+0xbc/0xf8
[ 7.913918] kvm_io_bus_write+0x48/0x80
[ 7.913921] io_mem_abort+0x128/0x288
[ 7.913924] kvm_handle_guest_abort+0x2c0/0xe88
[ 7.913927] handle_exit+0x6c/0x1d8
[ 7.913930] kvm_arch_vcpu_ioctl_run+0x454/0x6e8
[ 7.913932] kvm_vcpu_ioctl+0x310/0x9e0
[ 7.913935] do_vfs_ioctl+0x604/0xbd0
[ 7.913938] ksys_ioctl+0x78/0xa8
[ 7.913940] __arm64_sys_ioctl+0x1c/0x28
[ 7.913943] el0_svc_handler+0x7c/0x188
[ 7.913946] el0_sync_handler+0x138/0x258
[ 7.913948] el0_sync+0x140/0x180
[ 7.913952] Code: a8c87bfd d65f03c0 97fe9008 d503201f (f9400803)
[ 7.913954] ---[ end trace e0d0e4b407d388f3 ]---

Thanks,

> + if (!WARN_ON(ret)) {
> + /* Transfer pending state */
> + ret = irq_set_irqchip_state(irq->host_irq,
> + IRQCHIP_STATE_PENDING,
> + irq->pending_latch);
> + WARN_ON(ret);
> + irq->pending_latch = false;
> + }
> +
> + vgic_put_irq(vcpu->kvm, irq);
> + }
> +}
> +
> +static void vgic_v4_disable_vsgis(struct kvm_vcpu *vcpu)
> +{
> + int i;
> +
> + for (i = 0; i < VGIC_NR_SGIS; i++) {
> + struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
> + struct irq_desc *desc;
> + int ret;
> +
> + if (!irq->hw) {
> + vgic_put_irq(vcpu->kvm, irq);
> + continue;
> + }
> +
> + irq->hw = false;
> + ret = irq_get_irqchip_state(irq->host_irq,
> + IRQCHIP_STATE_PENDING,
> + &irq->pending_latch);
> + WARN_ON(ret);
> +
> + desc = irq_to_desc(irq->host_irq);
> + irq_domain_deactivate_irq(irq_desc_get_irq_data(desc));
> +
> + vgic_put_irq(vcpu->kvm, irq);
> + }
> +}
> +
> +/* Must be called with the kvm lock held */
> +void vgic_v4_configure_vsgis(struct kvm *kvm)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + struct kvm_vcpu *vcpu;
> + int i;
> +
> + kvm_arm_halt_guest(kvm);
> +
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + if (dist->nassgireq)
> + vgic_v4_enable_vsgis(vcpu);
> + else
> + vgic_v4_disable_vsgis(vcpu);
> + }
> +
> + kvm_arm_resume_guest(kvm);
> +}
> +
> /**
> * vgic_v4_init - Initialize the GICv4 data structures
> * @kvm: Pointer to the VM being initialized
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index c7fefd6b1c80..769e4802645e 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -316,5 +316,6 @@ void vgic_its_invalidate_cache(struct kvm *kvm);
> bool vgic_supports_direct_msis(struct kvm *kvm);
> int vgic_v4_init(struct kvm *kvm);
> void vgic_v4_teardown(struct kvm *kvm);
> +void vgic_v4_configure_vsgis(struct kvm *kvm);
>
> #endif
>