ata_piix: fix locking around SIDPR access

SIDPR window registers are shared across ports and as each access is done in two steps, accesses to different ports under EH may race. This primarily is caused by incorrect host locking in EH context and should be fixed by defining locking requirements for each EH operation which can be used during EH and enforcing them but for now work around the problem by adding a dedicated SIDPR lock and grabbing it for each SIDPR access.

Signed-off-by Tejun Heo <[email protected]>

Reported-by Mark Knecht <[email protected]>

Reported-by Paul Check <[email protected]>

Cc [email protected]

---
 drivers/ata/ata_piix.c |    8 ++++++++
 1 file changed, 8 insertions(+)

drivers/ata/ata_piix.c +8 -1

index 7409f98..3971bc0 100644
@@ -158,6 +158,7 @@ struct piix_map_db {
 struct piix_host_priv {
 	const int *map;
 	u32 saved_iocfg;
+	spinlock_t sidpr_lock;	/* FIXME: remove once locking in EH is fixed */
 	void __iomem *sidpr;
 };
 

@@ -951,12 +952,15 @@ static int piix_sidpr_scr_read(struct ata_link *link,
 			       unsigned int reg, u32 *val)
 {
 	struct piix_host_priv *hpriv = link->ap->host->private_data;
+	unsigned long flags;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
+	spin_lock_irqsave(&hpriv->sidpr_lock, flags);
 	piix_sidpr_sel(link, reg);
 	*val = ioread32(hpriv->sidpr + PIIX_SIDPR_DATA);
+	spin_unlock_irqrestore(&hpriv->sidpr_lock, flags);
 	return 0;
 }
 

@@ -964,12 +968,15 @@ static int piix_sidpr_scr_write(struct ata_link *link,
 				unsigned int reg, u32 val)
 {
 	struct piix_host_priv *hpriv = link->ap->host->private_data;
+	unsigned long flags;
 
 	if (reg >= ARRAY_SIZE(piix_sidx_map))
 		return -EINVAL;
 
+	spin_lock_irqsave(&hpriv->sidpr_lock, flags);
 	piix_sidpr_sel(link, reg);
 	iowrite32(val, hpriv->sidpr + PIIX_SIDPR_DATA);
+	spin_unlock_irqrestore(&hpriv->sidpr_lock, flags);
 	return 0;
 }
 

@@ -1566,6 +1573,7 @@ static int __devinit piix_init_one(struct pci_dev *pdev,
 	hpriv = devm_kzalloc(dev, sizeof(*hpriv), GFP_KERNEL);
 	if (!hpriv)
 		return -ENOMEM;
+	spin_lock_init(&hpriv->sidpr_lock);
 
 	/* Save IOCFG, this will be used for cable detection, quirk
 	 * detection and restoration on detach.  This is necessary
--

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SIDPR window registers are shared across ports and as each access is done in two steps, accesses to different ports under EH may race. This primarily is caused by incorrect host locking in EH context and should be fixed by defining locking requirements for each EH operation which can be used during EH and enforcing them but for now work around the problem by adding a dedicated SIDPR lock and grabbing it for each SIDPR access.

Signed-off-by Tejun Heo<[email protected]>

Reported-by Mark Knecht<[email protected]>

Reported-by Paul Check<[email protected]>

Cc [email protected]

---
  drivers/ata/ata_piix.c |    8 ++++++++
  1 file changed, 8 insertions(+)