From: Jean-Philippe Brucker jean-philippe@linaro.org
[ Upstream commit 59112e9c390be595224e427827475a6cd3726021 ]
Lockdep reports a circular lock dependency between the srcu and the config_lock:
[ 262.179917] -> #1 (&kvm->srcu){.+.+}-{0:0}: [ 262.182010] __synchronize_srcu+0xb0/0x224 [ 262.183422] synchronize_srcu_expedited+0x24/0x34 [ 262.184554] kvm_io_bus_register_dev+0x324/0x50c [ 262.185650] vgic_register_redist_iodev+0x254/0x398 [ 262.186740] vgic_v3_set_redist_base+0x3b0/0x724 [ 262.188087] kvm_vgic_addr+0x364/0x600 [ 262.189189] vgic_set_common_attr+0x90/0x544 [ 262.190278] vgic_v3_set_attr+0x74/0x9c [ 262.191432] kvm_device_ioctl+0x2a0/0x4e4 [ 262.192515] __arm64_sys_ioctl+0x7ac/0x1ba8 [ 262.193612] invoke_syscall.constprop.0+0x70/0x1e0 [ 262.195006] do_el0_svc+0xe4/0x2d4 [ 262.195929] el0_svc+0x44/0x8c [ 262.196917] el0t_64_sync_handler+0xf4/0x120 [ 262.198238] el0t_64_sync+0x190/0x194 [ 262.199224] [ 262.199224] -> #0 (&kvm->arch.config_lock){+.+.}-{3:3}: [ 262.201094] __lock_acquire+0x2b70/0x626c [ 262.202245] lock_acquire+0x454/0x778 [ 262.203132] __mutex_lock+0x190/0x8b4 [ 262.204023] mutex_lock_nested+0x24/0x30 [ 262.205100] vgic_mmio_write_v3_misc+0x5c/0x2a0 [ 262.206178] dispatch_mmio_write+0xd8/0x258 [ 262.207498] __kvm_io_bus_write+0x1e0/0x350 [ 262.208582] kvm_io_bus_write+0xe0/0x1cc [ 262.209653] io_mem_abort+0x2ac/0x6d8 [ 262.210569] kvm_handle_guest_abort+0x9b8/0x1f88 [ 262.211937] handle_exit+0xc4/0x39c [ 262.212971] kvm_arch_vcpu_ioctl_run+0x90c/0x1c04 [ 262.214154] kvm_vcpu_ioctl+0x450/0x12f8 [ 262.215233] __arm64_sys_ioctl+0x7ac/0x1ba8 [ 262.216402] invoke_syscall.constprop.0+0x70/0x1e0 [ 262.217774] do_el0_svc+0xe4/0x2d4 [ 262.218758] el0_svc+0x44/0x8c [ 262.219941] el0t_64_sync_handler+0xf4/0x120 [ 262.221110] el0t_64_sync+0x190/0x194
Note that the current report, which can be triggered by the vgic_irq kselftest, is a triple chain that includes slots_lock, but after inverting the slots_lock/config_lock dependency, the actual problem reported above remains.
In several places, the vgic code calls kvm_io_bus_register_dev(), which synchronizes the srcu, while holding config_lock (#1). And the MMIO handler takes the config_lock while holding the srcu read lock (#0).
Break dependency #1, by registering the distributor and redistributors without holding config_lock. The ITS also uses kvm_io_bus_register_dev() but already relies on slots_lock to serialize calls.
The distributor iodev is created on the first KVM_RUN call. Multiple threads will race for vgic initialization, and only the first one will see !vgic_ready() under the lock. To serialize those threads, rely on slots_lock rather than config_lock.
Redistributors are created earlier, through KVM_DEV_ARM_VGIC_GRP_ADDR ioctls and vCPU creation. Similarly, serialize the iodev creation with slots_lock, and the rest with config_lock.
Fixes: f00327731131 ("KVM: arm64: Use config_lock to protect vgic state") Signed-off-by: Jean-Philippe Brucker jean-philippe@linaro.org Reviewed-by: Oliver Upton oliver.upton@linux.dev Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20230518100914.2837292-2-jean-philippe@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kvm/vgic/vgic-init.c | 25 ++++++++++++++++----- arch/arm64/kvm/vgic/vgic-kvm-device.c | 10 +++++++-- arch/arm64/kvm/vgic/vgic-mmio-v3.c | 31 ++++++++++++++++++--------- arch/arm64/kvm/vgic/vgic-mmio.c | 9 ++------ arch/arm64/kvm/vgic/vgic-v2.c | 6 ------ arch/arm64/kvm/vgic/vgic-v3.c | 7 ------ 6 files changed, 51 insertions(+), 37 deletions(-)
diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 9d42c7cb2b588..c199ba2f192ef 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -235,9 +235,9 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu) * KVM io device for the redistributor that belongs to this VCPU. */ if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) { - mutex_lock(&vcpu->kvm->arch.config_lock); + mutex_lock(&vcpu->kvm->slots_lock); ret = vgic_register_redist_iodev(vcpu); - mutex_unlock(&vcpu->kvm->arch.config_lock); + mutex_unlock(&vcpu->kvm->slots_lock); } return ret; } @@ -446,11 +446,13 @@ int vgic_lazy_init(struct kvm *kvm) int kvm_vgic_map_resources(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; + gpa_t dist_base; int ret = 0;
if (likely(vgic_ready(kvm))) return 0;
+ mutex_lock(&kvm->slots_lock); mutex_lock(&kvm->arch.config_lock); if (vgic_ready(kvm)) goto out; @@ -463,13 +465,26 @@ int kvm_vgic_map_resources(struct kvm *kvm) else ret = vgic_v3_map_resources(kvm);
- if (ret) + if (ret) { __kvm_vgic_destroy(kvm); - else - dist->ready = true; + goto out; + } + dist->ready = true; + dist_base = dist->vgic_dist_base; + mutex_unlock(&kvm->arch.config_lock); + + ret = vgic_register_dist_iodev(kvm, dist_base, + kvm_vgic_global_state.type); + if (ret) { + kvm_err("Unable to register VGIC dist MMIO regions\n"); + kvm_vgic_destroy(kvm); + } + mutex_unlock(&kvm->slots_lock); + return ret;
out: mutex_unlock(&kvm->arch.config_lock); + mutex_unlock(&kvm->slots_lock); return ret; }
diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c index 07e727023deb7..bf4b3d9631ce1 100644 --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c @@ -102,7 +102,11 @@ static int kvm_vgic_addr(struct kvm *kvm, struct kvm_device_attr *attr, bool wri if (get_user(addr, uaddr)) return -EFAULT;
- mutex_lock(&kvm->arch.config_lock); + /* + * Since we can't hold config_lock while registering the redistributor + * iodevs, take the slots_lock immediately. + */ + mutex_lock(&kvm->slots_lock); switch (attr->attr) { case KVM_VGIC_V2_ADDR_TYPE_DIST: r = vgic_check_type(kvm, KVM_DEV_TYPE_ARM_VGIC_V2); @@ -182,6 +186,7 @@ static int kvm_vgic_addr(struct kvm *kvm, struct kvm_device_attr *attr, bool wri if (r) goto out;
+ mutex_lock(&kvm->arch.config_lock); if (write) { r = vgic_check_iorange(kvm, *addr_ptr, addr, alignment, size); if (!r) @@ -189,9 +194,10 @@ static int kvm_vgic_addr(struct kvm *kvm, struct kvm_device_attr *attr, bool wri } else { addr = *addr_ptr; } + mutex_unlock(&kvm->arch.config_lock);
out: - mutex_unlock(&kvm->arch.config_lock); + mutex_unlock(&kvm->slots_lock);
if (!r && !write) r = put_user(addr, uaddr); diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c index 472b18ac92a24..188d2187eede9 100644 --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c @@ -769,10 +769,13 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu) struct vgic_io_device *rd_dev = &vcpu->arch.vgic_cpu.rd_iodev; struct vgic_redist_region *rdreg; gpa_t rd_base; - int ret; + int ret = 0; + + lockdep_assert_held(&kvm->slots_lock); + mutex_lock(&kvm->arch.config_lock);
if (!IS_VGIC_ADDR_UNDEF(vgic_cpu->rd_iodev.base_addr)) - return 0; + goto out_unlock;
/* * We may be creating VCPUs before having set the base address for the @@ -782,10 +785,12 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu) */ rdreg = vgic_v3_rdist_free_slot(&vgic->rd_regions); if (!rdreg) - return 0; + goto out_unlock;
- if (!vgic_v3_check_base(kvm)) - return -EINVAL; + if (!vgic_v3_check_base(kvm)) { + ret = -EINVAL; + goto out_unlock; + }
vgic_cpu->rdreg = rdreg; vgic_cpu->rdreg_index = rdreg->free_index; @@ -799,16 +804,20 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu) rd_dev->nr_regions = ARRAY_SIZE(vgic_v3_rd_registers); rd_dev->redist_vcpu = vcpu;
- mutex_lock(&kvm->slots_lock); + mutex_unlock(&kvm->arch.config_lock); + ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, rd_base, 2 * SZ_64K, &rd_dev->dev); - mutex_unlock(&kvm->slots_lock); - if (ret) return ret;
+ /* Protected by slots_lock */ rdreg->free_index++; return 0; + +out_unlock: + mutex_unlock(&kvm->arch.config_lock); + return ret; }
static void vgic_unregister_redist_iodev(struct kvm_vcpu *vcpu) @@ -834,12 +843,10 @@ static int vgic_register_all_redist_iodevs(struct kvm *kvm) /* The current c failed, so iterate over the previous ones. */ int i;
- mutex_lock(&kvm->slots_lock); for (i = 0; i < c; i++) { vcpu = kvm_get_vcpu(kvm, i); vgic_unregister_redist_iodev(vcpu); } - mutex_unlock(&kvm->slots_lock); }
return ret; @@ -938,7 +945,9 @@ int vgic_v3_set_redist_base(struct kvm *kvm, u32 index, u64 addr, u32 count) { int ret;
+ mutex_lock(&kvm->arch.config_lock); ret = vgic_v3_alloc_redist_region(kvm, index, addr, count); + mutex_unlock(&kvm->arch.config_lock); if (ret) return ret;
@@ -950,8 +959,10 @@ int vgic_v3_set_redist_base(struct kvm *kvm, u32 index, u64 addr, u32 count) if (ret) { struct vgic_redist_region *rdreg;
+ mutex_lock(&kvm->arch.config_lock); rdreg = vgic_v3_rdist_region_from_index(kvm, index); vgic_v3_free_redist_region(rdreg); + mutex_unlock(&kvm->arch.config_lock); return ret; }
diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c index 1939c94e0b248..ff558c05e990c 100644 --- a/arch/arm64/kvm/vgic/vgic-mmio.c +++ b/arch/arm64/kvm/vgic/vgic-mmio.c @@ -1096,7 +1096,6 @@ int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address, enum vgic_type type) { struct vgic_io_device *io_device = &kvm->arch.vgic.dist_iodev; - int ret = 0; unsigned int len;
switch (type) { @@ -1114,10 +1113,6 @@ int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address, io_device->iodev_type = IODEV_DIST; io_device->redist_vcpu = NULL;
- mutex_lock(&kvm->slots_lock); - ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, dist_base_address, - len, &io_device->dev); - mutex_unlock(&kvm->slots_lock); - - return ret; + return kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, dist_base_address, + len, &io_device->dev); } diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c index 645648349c99b..7e9cdb78f7ce8 100644 --- a/arch/arm64/kvm/vgic/vgic-v2.c +++ b/arch/arm64/kvm/vgic/vgic-v2.c @@ -312,12 +312,6 @@ int vgic_v2_map_resources(struct kvm *kvm) return ret; }
- ret = vgic_register_dist_iodev(kvm, dist->vgic_dist_base, VGIC_V2); - if (ret) { - kvm_err("Unable to register VGIC MMIO regions\n"); - return ret; - } - if (!static_branch_unlikely(&vgic_v2_cpuif_trap)) { ret = kvm_phys_addr_ioremap(kvm, dist->vgic_cpu_base, kvm_vgic_global_state.vcpu_base, diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index 469d816f356f3..76af07e66d731 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -539,7 +539,6 @@ int vgic_v3_map_resources(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; struct kvm_vcpu *vcpu; - int ret = 0; unsigned long c;
kvm_for_each_vcpu(c, vcpu, kvm) { @@ -569,12 +568,6 @@ int vgic_v3_map_resources(struct kvm *kvm) return -EBUSY; }
- ret = vgic_register_dist_iodev(kvm, dist->vgic_dist_base, VGIC_V3); - if (ret) { - kvm_err("Unable to register VGICv3 dist MMIO regions\n"); - return ret; - } - if (kvm_vgic_global_state.has_gicv4_1) vgic_v4_configure_vsgis(kvm);