[PATCH] iommu/vt-d: fix missing lock in intel_pasid_replace_*() functions

[PATCH] iommu/vt-d: fix missing lock in intel_pasid_replace_*() functions

[Ziyi Guo]

intel_pasid_replace_first_level(), intel_pasid_replace_second_level(),
intel_pasid_replace_pass_through(), and intel_pasid_replace_nested()
call their respective pasid_pte_config_*() helpers before acquiring
iommu->lock. However, each config function has
lockdep_assert_held(&iommu->lock).

The corresponding intel_pasid_setup_*() functions correctly acquire
iommu->lock before calling the config helpers.

Let spin_lock(&iommu->lock) before the pasid_pte_config_*() calls to
fix the lockdep assertions and ensure consistent access to IOMMU state.

Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
---
 drivers/iommu/intel/pasid.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index 3e2255057079..dd4c8287d354 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -431,9 +431,8 @@ int intel_pasid_replace_first_level(struct intel_iommu *iommu,
 		return -EINVAL;
 	}
 
-	pasid_pte_config_first_level(iommu, &new_pte, fsptptr, did, flags);
-
 	spin_lock(&iommu->lock);
+	pasid_pte_config_first_level(iommu, &new_pte, fsptptr, did, flags);
 	pte = intel_pasid_get_entry(dev, pasid);
 	if (!pte) {
 		spin_unlock(&iommu->lock);
@@ -542,9 +541,8 @@ int intel_pasid_replace_second_level(struct intel_iommu *iommu,
 
 	did = domain_id_iommu(domain, iommu);
 
-	pasid_pte_config_second_level(iommu, &new_pte, domain, did);
-
 	spin_lock(&iommu->lock);
+	pasid_pte_config_second_level(iommu, &new_pte, domain, did);
 	pte = intel_pasid_get_entry(dev, pasid);
 	if (!pte) {
 		spin_unlock(&iommu->lock);
@@ -686,9 +684,8 @@ int intel_pasid_replace_pass_through(struct intel_iommu *iommu,
 	struct pasid_entry *pte, new_pte;
 	u16 did = FLPT_DEFAULT_DID;
 
-	pasid_pte_config_pass_through(iommu, &new_pte, did);
-
 	spin_lock(&iommu->lock);
+	pasid_pte_config_pass_through(iommu, &new_pte, did);
 	pte = intel_pasid_get_entry(dev, pasid);
 	if (!pte) {
 		spin_unlock(&iommu->lock);
@@ -882,9 +879,8 @@ int intel_pasid_replace_nested(struct intel_iommu *iommu,
 		return -EINVAL;
 	}
 
-	pasid_pte_config_nestd(iommu, &new_pte, s1_cfg, s2_domain, did);
-
 	spin_lock(&iommu->lock);
+	pasid_pte_config_nestd(iommu, &new_pte, s1_cfg, s2_domain, did);
 	pte = intel_pasid_get_entry(dev, pasid);
 	if (!pte) {
 		spin_unlock(&iommu->lock);
-- 
2.34.1

Re: [PATCH] iommu/vt-d: fix missing lock in intel_pasid_replace_*() functions

[Baolu Lu]

On 1/31/26 03:06, Ziyi Guo wrote:
> intel_pasid_replace_first_level(), intel_pasid_replace_second_level(),
> intel_pasid_replace_pass_through(), and intel_pasid_replace_nested()
> call their respective pasid_pte_config_*() helpers before acquiring
> iommu->lock. However, each config function has
> lockdep_assert_held(&iommu->lock).
> 
> The corresponding intel_pasid_setup_*() functions correctly acquire
> iommu->lock before calling the config helpers.
> 
> Let spin_lock(&iommu->lock) before the pasid_pte_config_*() calls to
> fix the lockdep assertions and ensure consistent access to IOMMU state.
> 
> Signed-off-by: Ziyi Guo<n7l8m4@u.northwestern.edu>
> ---
>   drivers/iommu/intel/pasid.c | 12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)

Thanks for the patch. It looks like this was addressed by commit
c3b1edea3791 ("iommu/vt-d: Fix race condition during PASID entry
replacement"), currently in iommu/next. Let me know if you think there
is still something missing.

Thanks,
baolu