@@ -1704,13 +1704,13 @@
iommu.strict= [ARM64] Configure TLB invalidation behaviour
Format: { "0" | "1" }
- 0 - Lazy mode.
+ 0 - Lazy mode (default).
Request that DMA unmap operations use deferred
invalidation of hardware TLBs, for increased
throughput at the cost of reduced device isolation.
Will fall back to strict mode if not supported by
the relevant IOMMU driver.
- 1 - Strict mode (default).
+ 1 - Strict mode.
DMA unmap operations invalidate IOMMU hardware TLBs
synchronously.
@@ -37,7 +37,7 @@
static struct kset *iommu_group_kset;
static DEFINE_IDA(iommu_group_ida);
static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA;
-static bool iommu_dma_strict __read_mostly = true;
+static bool iommu_dma_strict __read_mostly;
struct iommu_callback_data {
const struct iommu_ops *ops;
BugLink: https://bugs.launchpad.net/bugs/1902281 Relax the synchronous IOMMU TLB invalidation constraint by default to get a significant performance improvement on some AWS arm64 instance types. This is a performance vs security tradeoff and it is not suitable for the generic kernel. In the particular AWS environment it is reasonable to relax the constraint without realisticly introducing security flaws. Signed-off-by: Andrea Righi <andrea.righi@canonical.com> --- Documentation/admin-guide/kernel-parameters.txt | 4 ++-- drivers/iommu/iommu.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-)