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Subject[PATCH 1/1] iommu: Avoid unnecessary cache invalidations
Date
The iommu_create_device_direct_mappings() only needs to flush the caches
when the mappings are changed in the affected domain. This is not true
for non-DMA domains, or for devices attached to the domain that have no
reserved regions. To avoid unnecessary cache invalidations, add a check
before iommu_flush_iotlb_all().

Fixes: a48ce36e2786 ("iommu: Prevent RESV_DIRECT devices from blocking domains")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/iommu/iommu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 00d0a2b5d7dc..0cb676590bfa 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1114,7 +1114,8 @@ static int iommu_create_device_direct_mappings(struct iommu_domain *domain,

}

- iommu_flush_iotlb_all(domain);
+ if (!list_empty(&mappings) && iommu_is_dma_domain(domain))
+ iommu_flush_iotlb_all(domain);

out:
iommu_put_resv_regions(dev, &mappings);
--
2.34.1
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