[PATCH v5 1/2] hisi_acc_vfio_pci: fix NULL dereference in reset_prepare on PF passthrough

[Longfang Liu <liulongfang@huawei.com>]

When a PF is bound to the driver via driver_override and passed
through to a VM, its pf_qm stays NULL. The PCI error handler
reset_prepare() runs during open_device through
pci_try_reset_function(), before the mig_ops gate, and dereferences
the NULL pf_qm for the timeout log, crashing the kernel.

Move the mig_ops check to the entry of reset_prepare() and
aer_reset_done() so non-migration devices skip the QM_RESETTING
coordination. Also clear set_reset_flag together with QM_RESETTING
in aer_reset_done(); the flag was never cleared before, so a later
timed-out reset could release a foreign lock.

Fixes: b0eed085903e ("hisi_acc_vfio_pci: Add support for VFIO live migration")
Fixes: a22099ed7936f ("hisi_acc_vfio_pci: fix VF reset timeout issue")
Signed-off-by: Longfang Liu <liulongfang@huawei.com>
---
 drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
index 86362ec424a5..6a09252258b9 100644
--- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
+++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
@@ -1157,6 +1157,9 @@ static void hisi_acc_vf_pci_reset_prepare(struct pci_dev *pdev)
 	struct device *dev = &qm->pdev->dev;
 	u32 delay = 0;
 
+	if (!hisi_acc_vdev->core_device.vdev.mig_ops)
+		return;
+
 	/* All reset requests need to be queued for processing */
 	while (test_and_set_bit(QM_RESETTING, &qm->misc_ctl)) {
 		msleep(1);
@@ -1174,12 +1177,14 @@ static void hisi_acc_vf_pci_aer_reset_done(struct pci_dev *pdev)
 	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_drvdata(pdev);
 	struct hisi_qm *qm = hisi_acc_vdev->pf_qm;
 
-	if (hisi_acc_vdev->set_reset_flag)
-		clear_bit(QM_RESETTING, &qm->misc_ctl);
-
 	if (!hisi_acc_vdev->core_device.vdev.mig_ops)
 		return;
 
+	if (hisi_acc_vdev->set_reset_flag) {
+		clear_bit(QM_RESETTING, &qm->misc_ctl);
+		hisi_acc_vdev->set_reset_flag = false;
+	}
+
 	mutex_lock(&hisi_acc_vdev->state_mutex);
 	hisi_acc_vf_reset(hisi_acc_vdev);
 	mutex_unlock(&hisi_acc_vdev->state_mutex);
-- 
2.43.0