This is a note to let you know that I've just added the patch titled
KVM: arm64: vgic: Fix a circular locking issue
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-arm64-vgic-fix-a-circular-locking-issue.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bef0f4d7a2019ef71eec81416b1edec61b2008b6
Author: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
Date: Thu May 18 11:09:15 2023 +0100
KVM: arm64: vgic: Fix a circular locking issue
[ 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@xxxxxxxxxx>
Reviewed-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230518100914.2837292-2-jean-philippe@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);
