crypto: qat - protect interrupt mask CSRs with a spinlock

In the PF interrupt handler, the interrupt is disabled for a set of VFs
by writing to the interrupt source mask register, ERRMSK.
The interrupt is re-enabled in the bottom half handler by writing to the
same CSR. This is done through the functions enable_vf2pf_interrupts()
and disable_vf2pf_interrupts() which perform a read-modify-write
operation on the ERRMSK registers to mask and unmask the source of
interrupt.

There can be a race condition where the top half handler for one VF
interrupt runs just as the bottom half for another VF is about to
re-enable the interrupt. Depending on whether the top or bottom half
updates the CSR first, this would result either in a spurious interrupt
or in the interrupt not being re-enabled.

This patch protects the access of ERRMSK with a spinlock.

The functions adf_enable_vf2pf_interrupts() and
adf_disable_vf2pf_interrupts() have been changed to acquire a spin lock
before accessing and modifying the ERRMSK registers. These functions use
spin_lock_irqsave() to disable IRQs and avoid potential deadlocks.
In addition, the function adf_disable_vf2pf_interrupts_irq() has been
added. This uses spin_lock() and it is meant to be used in the top half
only.

Signed-off-by: Kanchana Velusamy <kanchanax.velusamy@intel.com>
Co-developed-by: Marco Chiappero <marco.chiappero@intel.com>
Signed-off-by: Marco Chiappero <marco.chiappero@intel.com>
Co-developed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Fiona Trahe <fiona.trahe@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qat/qat_c3xxx/adf_c3xxx_hw_data.c

@@ -161,6 +161,8 @@ static void adf_enable_ints(struct adf_accel_dev *accel_dev)
 
 static int adf_pf_enable_vf2pf_comms(struct adf_accel_dev *accel_dev)
 {
+	spin_lock_init(&accel_dev->pf.vf2pf_ints_lock);
+
 	return 0;
 }
 

drivers/crypto/qat/qat_c62x/adf_c62x_hw_data.c

@@ -163,6 +163,8 @@ static void adf_enable_ints(struct adf_accel_dev *accel_dev)
 
 static int adf_pf_enable_vf2pf_comms(struct adf_accel_dev *accel_dev)
 {
+	spin_lock_init(&accel_dev->pf.vf2pf_ints_lock);
+
 	return 0;
 }
 

drivers/crypto/qat/qat_common/adf_accel_devices.h

@@ -246,6 +246,8 @@ struct adf_accel_dev {
 	struct adf_accel_pci accel_pci_dev;
 	union {
 		struct {
+			/* protects VF2PF interrupts access */
+			spinlock_t vf2pf_ints_lock;
 			/* vf_info is non-zero when SR-IOV is init'ed */
 			struct adf_accel_vf_info *vf_info;
 		} pf;

drivers/crypto/qat/qat_common/adf_common_drv.h

@@ -193,6 +193,8 @@ int adf_sriov_configure(struct pci_dev *pdev, int numvfs);
 void adf_disable_sriov(struct adf_accel_dev *accel_dev);
 void adf_disable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
 				  u32 vf_mask);
+void adf_disable_vf2pf_interrupts_irq(struct adf_accel_dev *accel_dev,
+				      u32 vf_mask);
 void adf_enable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
 				 u32 vf_mask);
 void adf_enable_pf2vf_interrupts(struct adf_accel_dev *accel_dev);

drivers/crypto/qat/qat_common/adf_isr.c

@@ -103,7 +103,7 @@ static irqreturn_t adf_msix_isr_ae(int irq, void *dev_ptr)
 			int i;
 
 			/* Disable VF2PF interrupts for VFs with pending ints */
-			adf_disable_vf2pf_interrupts(accel_dev, vf_mask);
+			adf_disable_vf2pf_interrupts_irq(accel_dev, vf_mask);
 
 			/*
 			 * Handle VF2PF interrupt unless the VF is malicious and

drivers/crypto/qat/qat_common/adf_pf2vf_msg.c

@@ -11,7 +11,7 @@
 #define ADF_DH895XCC_ERRMSK5	(ADF_DH895XCC_EP_OFFSET + 0xDC)
 #define ADF_DH895XCC_ERRMSK5_VF2PF_U_MASK(vf_mask) (vf_mask >> 16)
 
-void adf_enable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
+static void __adf_enable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
 					  u32 vf_mask)
 {
 	struct adf_hw_device_data *hw_data = accel_dev->hw_device;
@@ -35,7 +35,17 @@ void adf_enable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
 	}
 }
 
-void adf_disable_vf2pf_interrupts(struct adf_accel_dev *accel_dev, u32 vf_mask)
+void adf_enable_vf2pf_interrupts(struct adf_accel_dev *accel_dev, u32 vf_mask)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&accel_dev->pf.vf2pf_ints_lock, flags);
+	__adf_enable_vf2pf_interrupts(accel_dev, vf_mask);
+	spin_unlock_irqrestore(&accel_dev->pf.vf2pf_ints_lock, flags);
+}
+
+static void __adf_disable_vf2pf_interrupts(struct adf_accel_dev *accel_dev,
+					   u32 vf_mask)
 {
 	struct adf_hw_device_data *hw_data = accel_dev->hw_device;
 	struct adf_bar *pmisc =
@@ -58,6 +68,22 @@ void adf_disable_vf2pf_interrupts(struct adf_accel_dev *accel_dev, u32 vf_mask)
 	}
 }
 
+void adf_disable_vf2pf_interrupts(struct adf_accel_dev *accel_dev, u32 vf_mask)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&accel_dev->pf.vf2pf_ints_lock, flags);
+	__adf_disable_vf2pf_interrupts(accel_dev, vf_mask);
+	spin_unlock_irqrestore(&accel_dev->pf.vf2pf_ints_lock, flags);
+}
+
+void adf_disable_vf2pf_interrupts_irq(struct adf_accel_dev *accel_dev, u32 vf_mask)
+{
+	spin_lock(&accel_dev->pf.vf2pf_ints_lock);
+	__adf_disable_vf2pf_interrupts(accel_dev, vf_mask);
+	spin_unlock(&accel_dev->pf.vf2pf_ints_lock);
+}
+
 static int __adf_iov_putmsg(struct adf_accel_dev *accel_dev, u32 msg, u8 vf_nr)
 {
 	struct adf_accel_pci *pci_info = &accel_dev->accel_pci_dev;
@@ -264,6 +290,7 @@ void adf_vf2pf_req_hndl(struct adf_accel_vf_info *vf_info)
 
 	/* re-enable interrupt on PF from this VF */
 	adf_enable_vf2pf_interrupts(accel_dev, (1 << vf_nr));
+
 	return;
 err:
 	dev_dbg(&GET_DEV(accel_dev), "Unknown message from VF%d (0x%x);\n",

drivers/crypto/qat/qat_dh895xcc/adf_dh895xcc_hw_data.c

@@ -182,6 +182,8 @@ static void adf_enable_ints(struct adf_accel_dev *accel_dev)
 
 static int adf_pf_enable_vf2pf_comms(struct adf_accel_dev *accel_dev)
 {
+	spin_lock_init(&accel_dev->pf.vf2pf_ints_lock);
+
 	return 0;
 }