i40e: add locking around VF reset

During VF deallocation, we need to lock out the VF reset code. However,
we cannot depend on simply masking the interrupt, as this does not lock
out the service task, which can still call the reset routine. Instead,
leave the interrupt enabled, but add locking around the VF disable and
reset routines.

For the disable code, we wait to get the lock, as the reset code will
take a finite amount of time to run. For the reset code, we just return
if we fail to get the lock. Since we know that the VFs are being
disabled, we don't need to handle the reset.
This fixes a panic when disabling SR-IOV.

Change-ID: Iea0a6cdef35c331f48c6d5b2f8e6f0e86322e7d8
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e.h

@@ -148,6 +148,7 @@ enum i40e_state_t {
 	__I40E_FD_FLUSH_REQUESTED,
 	__I40E_RESET_FAILED,
 	__I40E_PORT_TX_SUSPENDED,
+	__I40E_VF_DISABLE,
 };
 
 enum i40e_interrupt_policy {

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c

@@ -647,6 +647,9 @@ void i40e_reset_vf(struct i40e_vf *vf, bool flr)
 	int i;
 	u32 reg;
 
+	if (test_and_set_bit(__I40E_VF_DISABLE, &pf->state))
+		return;
+
 	/* warn the VF */
 	clear_bit(I40E_VF_STAT_ACTIVE, &vf->vf_states);
 
@@ -706,6 +709,7 @@ complete_reset:
 	/* tell the VF the reset is done */
 	wr32(hw, I40E_VFGEN_RSTAT1(vf->vf_id), I40E_VFR_VFACTIVE);
 	i40e_flush(hw);
+	clear_bit(__I40E_VF_DISABLE, &pf->state);
 }
 
 /**
@@ -790,6 +794,8 @@ void i40e_free_vfs(struct i40e_pf *pf)
 
 	if (!pf->vf)
 		return;
+	while (test_and_set_bit(__I40E_VF_DISABLE, &pf->state))
+		usleep_range(1000, 2000);
 
 	/* Disable IOV before freeing resources. This lets any VF drivers
 	 * running in the host get themselves cleaned up before we yank
@@ -800,9 +806,6 @@ void i40e_free_vfs(struct i40e_pf *pf)
 
 	msleep(20); /* let any messages in transit get finished up */
 
-	/* Disable interrupt 0 so we don't try to handle the VFLR. */
-	i40e_irq_dynamic_disable_icr0(pf);
-
 	/* free up vf resources */
 	tmp = pf->num_alloc_vfs;
 	pf->num_alloc_vfs = 0;
@@ -834,9 +837,7 @@ void i40e_free_vfs(struct i40e_pf *pf)
 		dev_warn(&pf->pdev->dev,
 			 "unable to disable SR-IOV because VFs are assigned.\n");
 	}
-
-	/* Re-enable interrupt 0. */
-	i40e_irq_dynamic_enable_icr0(pf);
+	clear_bit(__I40E_VF_DISABLE, &pf->state);
 }
 
 #ifdef CONFIG_PCI_IOV