linux-kernel - [PATCH v3 vfio 1/3] pds/vfio: Fix spinlock bad magic BUG

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Date:   Fri, 27 Oct 2023 15:36:49 -0700
From:   Brett Creeley <brett.creeley@....com>
To:     <jgg@...pe.ca>, <yishaih@...dia.com>,
        <shameerali.kolothum.thodi@...wei.com>, <kevin.tian@...el.com>,
        <alex.williamson@...hat.com>, <dan.carpenter@...aro.org>
CC:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <brett.creeley@....com>, <shannon.nelson@....com>
Subject: [PATCH v3 vfio 1/3] pds/vfio: Fix spinlock bad magic BUG

The following BUG was found when running on a kernel with
CONFIG_DEBUG_SPINLOCK=y set:

BUG: spinlock bad magic on CPU#2, bash/2481
 lock: 0xffff8d6052a88f50, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
Call Trace:
 <TASK>
 dump_stack_lvl+0x36/0x50
 do_raw_spin_lock+0x79/0xc0
 pds_vfio_reset+0x1d/0x60 [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

As shown, the .magic: 00000000, does not match the expected value. This
is because spin_lock_init() is never called for the reset_lock. Fix
this by calling spin_lock_init(&pds_vfio->reset_lock) when initializing
the device.

Signed-off-by: Brett Creeley <brett.creeley@....com>
Reviewed-by: Shannon Nelson <shannon.nelson@....com>
---
 drivers/vfio/pci/pds/vfio_dev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/vfio/pci/pds/vfio_dev.c b/drivers/vfio/pci/pds/vfio_dev.c
index 649b18ee394b..c351f588fa13 100644
--- a/drivers/vfio/pci/pds/vfio_dev.c
+++ b/drivers/vfio/pci/pds/vfio_dev.c
@@ -155,6 +155,8 @@ static int pds_vfio_init_device(struct vfio_device *vdev)
 
 	pds_vfio->vf_id = vf_id;
 
+	spin_lock_init(&pds_vfio->reset_lock);
+
 	vdev->migration_flags = VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_P2P;
 	vdev->mig_ops = &pds_vfio_lm_ops;
 	vdev->log_ops = &pds_vfio_log_ops;
-- 
2.17.1