diff options
author | Jean-Philippe Brucker <jean-philippe@linaro.org> | 2023-05-18 12:09:15 +0200 |
---|---|---|
committer | Marc Zyngier <maz@kernel.org> | 2023-05-19 11:20:00 +0200 |
commit | 59112e9c390be595224e427827475a6cd3726021 (patch) | |
tree | 658593c6cc5aef9755824dd4a40f4b83c463244f /arch/arm64/kvm/vgic/vgic-mmio-v3.c | |
parent | Merge branch kvm-arm64/pgtable-fixes-6.4 into kvmarm-master/fixes (diff) | |
download | linux-59112e9c390be595224e427827475a6cd3726021.tar.xz linux-59112e9c390be595224e427827475a6cd3726021.zip |
KVM: arm64: vgic: Fix a circular locking issue
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
Diffstat (limited to 'arch/arm64/kvm/vgic/vgic-mmio-v3.c')
-rw-r--r-- | arch/arm64/kvm/vgic/vgic-mmio-v3.c | 31 |
1 files changed, 21 insertions, 10 deletions
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c index 472b18ac92a2..188d2187eede 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; } |