[PATCH v2 11/19] iommu/arm-smmu-v3: Do not change the STE twice during arm_smmu_attach_dev()

[Jason Gunthorpe]

This was needed because the STE code required the STE to be in
ABORT/BYPASS inorder to program a cdtable or S2 STE. Now that the STE code
can automatically handle all transitions we can remove this step
from the attach_dev flow.

A few small bugs exist because of this:

1) If the core code does BLOCKED -> UNMANAGED with disable_bypass=false
   then there will be a moment where the STE points at BYPASS. Since
   this can be done by VFIO/IOMMUFD it is a small security race.

2) If the core code does IDENTITY -> DMA then any IOMMU_RESV_DIRECT
   regions will temporarily become BLOCKED. We'd like drivers to
   work in a way that allows IOMMU_RESV_DIRECT to be continuously
   functional during these transitions.

Make arm_smmu_release_device() put the STE back to the correct
ABORT/BYPASS setting. Fix a bug where a IOMMU_RESV_DIRECT was ignored on
this path.

Notice this subtly depends on the prior arm_smmu_asid_lock change as the
STE must be put to non-paging before removing the device for the linked
list to avoid races with arm_smmu_share_asid().

Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 4b157c2ddf9a80..f70862806211de 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2482,7 +2482,6 @@ static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
 static void arm_smmu_detach_dev(struct arm_smmu_master *master)
 {
 	unsigned long flags;
-	struct arm_smmu_ste target;
 	struct arm_smmu_domain *smmu_domain = master->domain;
 
 	if (!smmu_domain)
@@ -2496,11 +2495,6 @@ static void arm_smmu_detach_dev(struct arm_smmu_master *master)
 
 	master->domain = NULL;
 	master->ats_enabled = false;
-	if (disable_bypass)
-		arm_smmu_make_abort_ste(&target);
-	else
-		arm_smmu_make_bypass_ste(&target);
-	arm_smmu_install_ste_for_dev(master, &target);
 	/*
 	 * Clearing the CD entry isn't strictly required to detach the domain
 	 * since the table is uninstalled anyway, but it helps avoid confusion
@@ -2852,9 +2846,18 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
 static void arm_smmu_release_device(struct device *dev)
 {
 	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+	struct arm_smmu_ste target;
 
 	if (WARN_ON(arm_smmu_master_sva_enabled(master)))
 		iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
+
+	/* Put the STE back to what arm_smmu_init_strtab() sets */
+	if (disable_bypass && !dev->iommu->require_direct)
+		arm_smmu_make_abort_ste(&target);
+	else
+		arm_smmu_make_bypass_ste(&target);
+	arm_smmu_install_ste_for_dev(master, &target);
+
 	arm_smmu_detach_dev(master);
 	arm_smmu_disable_pasid(master);
 	arm_smmu_remove_master(master);
-- 
2.42.0