Commit d88cc962 authored by Brett Creeley's avatar Brett Creeley Committed by Zheng Zengkai
Browse files

vfio/pds: Fix possible sleep while in atomic context 

stable inclusion
from stable-v6.6.5
commit 72654bc1d404e05ab7e7c26cfbc966f5cd63288b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=72654bc1d404e05ab7e7c26cfbc966f5cd63288b



--------------------------------

[ 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: default avatarDan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/kvm/1f9bc27b-3de9-4891-9687-ba2820c1b390@moroto.mountain/


Fixes: bb500dbe ("vfio/pds: Add VFIO live migration support")
Signed-off-by: default avatarBrett Creeley <brett.creeley@amd.com>
Reviewed-by: default avatarShannon Nelson <shannon.nelson@amd.com>
Link: https://lore.kernel.org/r/20231122192532.25791-3-brett.creeley@amd.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent a80f268b

drivers/vfio/pci/pds/pci_drv.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

	}

}

drivers/vfio/pci/pds/vfio_dev.c

+8 −6
Original line number Diff line number Diff line
@@ -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);

}

drivers/vfio/pci/pds/vfio_dev.h

+1 −1
Original line number Diff line number Diff line
@@ -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;