This is a note to let you know that I've just added the patch titled
vfio/pds: Fix possible sleep while in atomic context
to the 6.6-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:
vfio-pds-fix-possible-sleep-while-in-atomic-context.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d223bcc6cae7ee99296be2d5e969b2d07e92f00c
Author: Brett Creeley <brett.creeley@xxxxxxx>
Date: Wed Nov 22 11:25:32 2023 -0800
vfio/pds: Fix possible sleep while in atomic context
[ Upstream commit ae2667cd8a479bb5abd6e24c12fcc9ef5bc06d75 ]
The driver could possibly sleep while in atomic context resulting
in the following call trace while CONFIG_DEBUG_ATOMIC_SLEEP=y is
set:
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2817, name: bash
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
Call Trace:
<TASK>
dump_stack_lvl+0x36/0x50
__might_resched+0x123/0x170
mutex_lock+0x1e/0x50
pds_vfio_put_lm_file+0x1e/0xa0 [pds_vfio_pci]
pds_vfio_put_save_file+0x19/0x30 [pds_vfio_pci]
pds_vfio_state_mutex_unlock+0x2e/0x80 [pds_vfio_pci]
pci_reset_function+0x4b/0x70
reset_store+0x5b/0xa0
kernfs_fop_write_iter+0x137/0x1d0
vfs_write+0x2de/0x410
ksys_write+0x5d/0xd0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
This can happen if pds_vfio_put_restore_file() and/or
pds_vfio_put_save_file() grab the mutex_lock(&lm_file->lock)
while the spin_lock(&pds_vfio->reset_lock) is held, which can
happen during while calling pds_vfio_state_mutex_unlock().
Fix this by changing the reset_lock to reset_mutex so there are no such
conerns. Also, make sure to destroy the reset_mutex in the driver specific
VFIO device release function.
This also fixes a spinlock bad magic BUG that was caused
by not calling spinlock_init() on the reset_lock. Since, the lock is
being changed to a mutex, make sure to call mutex_init() on it.
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Closes: https://lore.kernel.org/kvm/1f9bc27b-3de9-4891-9687-ba2820c1b390@moroto.mountain/
Fixes: bb500dbe2ac6 ("vfio/pds: Add VFIO live migration support")
Signed-off-by: Brett Creeley <brett.creeley@xxxxxxx>
Reviewed-by: Shannon Nelson <shannon.nelson@xxxxxxx>
Link: https://lore.kernel.org/r/20231122192532.25791-3-brett.creeley@xxxxxxx
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/vfio/pci/pds/pci_drv.c b/drivers/vfio/pci/pds/pci_drv.c
index ab4b5958e4131..caffa1a2cf591 100644
--- a/drivers/vfio/pci/pds/pci_drv.c
+++ b/drivers/vfio/pci/pds/pci_drv.c
@@ -55,10 +55,10 @@ static void pds_vfio_recovery(struct pds_vfio_pci_device *pds_vfio)
* VFIO_DEVICE_STATE_RUNNING.
*/
if (deferred_reset_needed) {
- spin_lock(&pds_vfio->reset_lock);
+ mutex_lock(&pds_vfio->reset_mutex);
pds_vfio->deferred_reset = true;
pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_ERROR;
- spin_unlock(&pds_vfio->reset_lock);
+ mutex_unlock(&pds_vfio->reset_mutex);
}
}
diff --git a/drivers/vfio/pci/pds/vfio_dev.c b/drivers/vfio/pci/pds/vfio_dev.c
index 8c9fb87b13e1d..4c351c59d05a9 100644
--- a/drivers/vfio/pci/pds/vfio_dev.c
+++ b/drivers/vfio/pci/pds/vfio_dev.c
@@ -29,7 +29,7 @@ struct pds_vfio_pci_device *pds_vfio_pci_drvdata(struct pci_dev *pdev)
void pds_vfio_state_mutex_unlock(struct pds_vfio_pci_device *pds_vfio)
{
again:
- spin_lock(&pds_vfio->reset_lock);
+ mutex_lock(&pds_vfio->reset_mutex);
if (pds_vfio->deferred_reset) {
pds_vfio->deferred_reset = false;
if (pds_vfio->state == VFIO_DEVICE_STATE_ERROR) {
@@ -39,23 +39,23 @@ void pds_vfio_state_mutex_unlock(struct pds_vfio_pci_device *pds_vfio)
}
pds_vfio->state = pds_vfio->deferred_reset_state;
pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_RUNNING;
- spin_unlock(&pds_vfio->reset_lock);
+ mutex_unlock(&pds_vfio->reset_mutex);
goto again;
}
mutex_unlock(&pds_vfio->state_mutex);
- spin_unlock(&pds_vfio->reset_lock);
+ mutex_unlock(&pds_vfio->reset_mutex);
}
void pds_vfio_reset(struct pds_vfio_pci_device *pds_vfio)
{
- spin_lock(&pds_vfio->reset_lock);
+ mutex_lock(&pds_vfio->reset_mutex);
pds_vfio->deferred_reset = true;
pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_RUNNING;
if (!mutex_trylock(&pds_vfio->state_mutex)) {
- spin_unlock(&pds_vfio->reset_lock);
+ mutex_unlock(&pds_vfio->reset_mutex);
return;
}
- spin_unlock(&pds_vfio->reset_lock);
+ mutex_unlock(&pds_vfio->reset_mutex);
pds_vfio_state_mutex_unlock(pds_vfio);
}
@@ -156,6 +156,7 @@ static int pds_vfio_init_device(struct vfio_device *vdev)
pds_vfio->vf_id = vf_id;
mutex_init(&pds_vfio->state_mutex);
+ mutex_init(&pds_vfio->reset_mutex);
vdev->migration_flags = VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_P2P;
vdev->mig_ops = &pds_vfio_lm_ops;
@@ -177,6 +178,7 @@ static void pds_vfio_release_device(struct vfio_device *vdev)
vfio_coredev.vdev);
mutex_destroy(&pds_vfio->state_mutex);
+ mutex_destroy(&pds_vfio->reset_mutex);
vfio_pci_core_release_dev(vdev);
}
diff --git a/drivers/vfio/pci/pds/vfio_dev.h b/drivers/vfio/pci/pds/vfio_dev.h
index b8f2d667608f3..e7b01080a1ec3 100644
--- a/drivers/vfio/pci/pds/vfio_dev.h
+++ b/drivers/vfio/pci/pds/vfio_dev.h
@@ -18,7 +18,7 @@ struct pds_vfio_pci_device {
struct pds_vfio_dirty dirty;
struct mutex state_mutex; /* protect migration state */
enum vfio_device_mig_state state;
- spinlock_t reset_lock; /* protect reset_done flow */
+ struct mutex reset_mutex; /* protect reset_done flow */
u8 deferred_reset;
enum vfio_device_mig_state deferred_reset_state;
struct notifier_block nb;
