[PATCH v3 4/9] iommu/vt-d: Make pasid setup helpers support modifying present pasid entry

[Yi Liu <yi.l.liu@xxxxxxxxx>]

To handle domain replacement, the set_dev_pasid() op needs to modify a
present pasid entry.

A natural way to implement the set_dev_pasid() op is to reuse the logic
of remove_dev_pasid() in the beginning to remove the old configuration.
Then set up the new pasid entry. Roll back to the old domain if it fails
to set up the new pasid entry. This needs to invoke the set_dev_pasid op
of the old domain. While this breaks the iommu layering a bit.

An alternative is implementing the set_dev_pasid() without rollback to the
old domain. This requires putting all the pasid entry modifications in
the pasid setup helpers. While the set_dev_pasid() op calls the helpers when
all the preparation work such as memory allocation, and sanity check has been
done.

To support modifying present pasid entry, the setup helpers needs to call
intel_pasid_tear_down_entry() to destroy the old configuration, which also
includes the necessary cache flushing and PRQ draining.

Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
 drivers/iommu/intel/pasid.c | 61 +++++++++++++------------------------
 1 file changed, 21 insertions(+), 40 deletions(-)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index 336f9425214c..ce0a3bf701df 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -321,18 +321,13 @@ int intel_pasid_setup_first_level(struct intel_iommu *iommu,
 		return -EINVAL;
 	}
 
-	spin_lock(&iommu->lock);
-	pte = intel_pasid_get_entry(dev, pasid);
-	if (!pte) {
-		spin_unlock(&iommu->lock);
+	/* Destroy the old configuration if it already exists */
+	pte = intel_pasid_tear_down_entry(iommu, dev, pasid,
+					  INTEL_PASID_TEARDOWN_DRAIN_PRQ);
+	if (!pte)
 		return -ENODEV;
-	}
-
-	if (pasid_pte_is_present(pte)) {
-		spin_unlock(&iommu->lock);
-		return -EBUSY;
-	}
 
+	spin_lock(&iommu->lock);
 	pasid_clear_entry(pte);
 
 	/* Setup the first level page table pointer: */
@@ -407,21 +402,16 @@ int intel_pasid_setup_second_level(struct intel_iommu *iommu,
 		return -EINVAL;
 	}
 
+	/* Destroy the old configuration if it already exists */
+	pte = intel_pasid_tear_down_entry(iommu, dev, pasid,
+					  INTEL_PASID_TEARDOWN_DRAIN_PRQ);
+	if (!pte)
+		return -ENODEV;
+
 	pgd_val = virt_to_phys(pgd);
 	did = domain_id_iommu(domain, iommu);
 
 	spin_lock(&iommu->lock);
-	pte = intel_pasid_get_entry(dev, pasid);
-	if (!pte) {
-		spin_unlock(&iommu->lock);
-		return -ENODEV;
-	}
-
-	if (pasid_pte_is_present(pte)) {
-		spin_unlock(&iommu->lock);
-		return -EBUSY;
-	}
-
 	pasid_clear_entry(pte);
 	pasid_set_domain_id(pte, did);
 	pasid_set_slptr(pte, pgd_val);
@@ -518,18 +508,13 @@ int intel_pasid_setup_pass_through(struct intel_iommu *iommu,
 	u16 did = FLPT_DEFAULT_DID;
 	struct pasid_entry *pte;
 
-	spin_lock(&iommu->lock);
-	pte = intel_pasid_get_entry(dev, pasid);
-	if (!pte) {
-		spin_unlock(&iommu->lock);
+	/* Destroy the old configuration if it already exists */
+	pte = intel_pasid_tear_down_entry(iommu, dev, pasid,
+					  INTEL_PASID_TEARDOWN_DRAIN_PRQ);
+	if (!pte)
 		return -ENODEV;
-	}
-
-	if (pasid_pte_is_present(pte)) {
-		spin_unlock(&iommu->lock);
-		return -EBUSY;
-	}
 
+	spin_lock(&iommu->lock);
 	pasid_clear_entry(pte);
 	pasid_set_domain_id(pte, did);
 	pasid_set_address_width(pte, iommu->agaw);
@@ -634,17 +619,13 @@ int intel_pasid_setup_nested(struct intel_iommu *iommu, struct device *dev,
 		return -EINVAL;
 	}
 
-	spin_lock(&iommu->lock);
-	pte = intel_pasid_get_entry(dev, pasid);
-	if (!pte) {
-		spin_unlock(&iommu->lock);
+	/* Destroy the old configuration if it already exists */
+	pte = intel_pasid_tear_down_entry(iommu, dev, pasid,
+					  INTEL_PASID_TEARDOWN_DRAIN_PRQ);
+	if (!pte)
 		return -ENODEV;
-	}
-	if (pasid_pte_is_present(pte)) {
-		spin_unlock(&iommu->lock);
-		return -EBUSY;
-	}
 
+	spin_lock(&iommu->lock);
 	pasid_clear_entry(pte);
 
 	if (s1_cfg->addr_width == ADDR_WIDTH_5LEVEL)
-- 
2.34.1