On Tue, Jan 14, 2020 at 03:25:39PM +0000, Will Deacon wrote:

On Thu, Dec 19, 2019 at 05:30:31PM +0100, Jean-Philippe Brucker wrote:

quoted

Let add_device() clean up after itself. The iommu_bus_init() function
does call remove_device() on error, but other sites (e.g. of_iommu) do
not.

Don't free level-2 stream tables because we'd have to track if we
allocated each of them or if they are used by other endpoints. It's not
worth the hassle since they are managed resources.

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <redacted>
---
 drivers/iommu/arm-smmu-v3.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

I think this is alright, with one caveat relating to:


	/*
	 * We _can_ actually withstand dodgy bus code re-calling add_device()
	 * without an intervening remove_device()/of_xlate() sequence, but
	 * we're not going to do so quietly...
	 */
	if (WARN_ON_ONCE(fwspec->iommu_priv)) {
		master = fwspec->iommu_priv;
		smmu = master->smmu;
	} ...


which may be on shakey ground if the subsequent add_device() call can fail
and free stuff that the first one allocated. At least, I don't know what
we're trying to support with this, so it's hard to tell whether or not it
still works as intended after your change.

How is this supposed to work? I don't recall ever seeing that WARN fire,
so can we just remove this and bail instead? Robin?

Something like below before your changes...

FWIW, I've written this as a patch locally, since I'd like to apply it
on top of v5 of your series.

Will

--->8

From 6029102f406d4db5e7a465da5fd2e08a5b12c532 Mon Sep 17 00:00:00 2001
From: Will Deacon <will@kernel.org>
Date: Wed, 15 Jan 2020 15:35:16 +0000
Subject: [PATCH] iommu/arm-smmu-v3: Return -EBUSY when trying to re-add a
 device

Although we WARN in arm_smmu_add_device() if the device being added has
been added already without a subsequent call to arm_smmu_remove_device(),
we still continue half-heartedly, initialising the stream-table for any
new StreamIDs that may have magically appeared and re-establishing device
links that should still be there from last time.

Given that calling ->add_device() twice without removing the device in the
meantime is indicative of an error in the caller, just return -EBUSY after
warning.

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Jean Philippe-Brucker <redacted>
Signed-off-by: Will Deacon <will@kernel.org>
---
 drivers/iommu/arm-smmu-v3.c | 37 ++++++++++++++++---------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index efa326601308..cc26e1323da3 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c

@@ -2841,28 +2841,23 @@ static int arm_smmu_add_device(struct device *dev)
 
 	if (!fwspec || fwspec->ops != &arm_smmu_ops)
 		return -ENODEV;
-	/*
-	 * We _can_ actually withstand dodgy bus code re-calling add_device()
-	 * without an intervening remove_device()/of_xlate() sequence, but
-	 * we're not going to do so quietly...
-	 */
-	if (WARN_ON_ONCE(fwspec->iommu_priv)) {
-		master = fwspec->iommu_priv;
-		smmu = master->smmu;
-	} else {
-		smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode);
-		if (!smmu)
-			return -ENODEV;
-		master = kzalloc(sizeof(*master), GFP_KERNEL);
-		if (!master)
-			return -ENOMEM;
 
-		master->dev = dev;
-		master->smmu = smmu;
-		master->sids = fwspec->ids;
-		master->num_sids = fwspec->num_ids;
-		fwspec->iommu_priv = master;
-	}
+	if (WARN_ON_ONCE(fwspec->iommu_priv))
+		return -EBUSY;
+
+	smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode);
+	if (!smmu)
+		return -ENODEV;
+
+	master = kzalloc(sizeof(*master), GFP_KERNEL);
+	if (!master)
+		return -ENOMEM;
+
+	master->dev = dev;
+	master->smmu = smmu;
+	master->sids = fwspec->ids;
+	master->num_sids = fwspec->num_ids;
+	fwspec->iommu_priv = master;
 
 	/* Check the SIDs are in range of the SMMU and our stream table */
 	for (i = 0; i < master->num_sids; i++) {

-- 
2.25.0.rc1.283.g88dfdc4193-goog


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