releases/6.12.75/iommu-vt-d-avoid-draining-prq-in-sva-mm-release-path.patch

From 68fbed3bf41b19b4787b828fcf8a77ff9ef1aba0 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Fri, 13 Dec 2024 09:17:52 +0800
Subject: iommu/vt-d: Avoid draining PRQ in sva mm release path

From: Lu Baolu <baolu.lu@linux.intel.com>

[ Upstream commit dda2b8c3c6ccc50deae65cc75f246577348e2ec5 ]

When a PASID is used for SVA by a device, it's possible that the PASID
entry is cleared before the device flushes all ongoing DMA requests and
removes the SVA domain. This can occur when an exception happens and the
process terminates before the device driver stops DMA and calls the
iommu driver to unbind the PASID.

There's no need to drain the PRQ in the mm release path. Instead, the PRQ
will be drained in the SVA unbind path.

Unfortunately, commit c43e1ccdebf2 ("iommu/vt-d: Drain PRQs when domain
removed from RID") changed this behavior by unconditionally draining the
PRQ in intel_pasid_tear_down_entry(). This can lead to a potential
sleeping-in-atomic-context issue.

Smatch static checker warning:

	drivers/iommu/intel/prq.c:95 intel_iommu_drain_pasid_prq()
	warn: sleeping in atomic context

To avoid this issue, prevent draining the PRQ in the SVA mm release path
and restore the previous behavior.

Fixes: c43e1ccdebf2 ("iommu/vt-d: Drain PRQs when domain removed from RID")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-iommu/c5187676-2fa2-4e29-94e0-4a279dc88b49@stanley.mountain/
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20241212021529.1104745-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Stable-dep-of: 75ed00055c05 ("iommu/vt-d: Clear Present bit before tearing down PASID entry")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/intel/pasid.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index 4e4d167720ba8..57969ba2d3975 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -266,7 +266,8 @@ void intel_pasid_tear_down_entry(struct intel_iommu *iommu, struct device *dev,
 		iommu->flush.flush_iotlb(iommu, did, 0, 0, DMA_TLB_DSI_FLUSH);
 
 	devtlb_invalidation_with_pasid(iommu, dev, pasid);
-	intel_iommu_drain_pasid_prq(dev, pasid);
+	if (!fault_ignore)
+		intel_iommu_drain_pasid_prq(dev, pasid);
 }
 
 /*
-- 
2.51.0