Hi All, This patch series adds adding initial support for eliding break-before-make requirements on systems that support BBML2 and additionally guarantee to never raise a conflict abort. This support elides a TLB invalidation in contpte_convert(). This leads to a 12% improvement when executing a microbenchmark designed to force the pathological path where contpte_convert() gets called. This represents an 80% reduction in the cost of calling contpte_convert(). This series is based on v6.14-rc4 (d082ecbc71e9). Patch 1 implements an allow-list of cpus that support BBML2, but with the additional constraint of never causing TLB conflict aborts. We settled on this constraint because we will use the feature for kernel mappings in the future, for which we cannot handle conflict aborts safely. Yang Shi has a series at [1] that aims to use BBML2 to enable splitting the linear map at runtime. This series partially overlaps with it to add the cpu feature. We believe this series is fully compatible with Yang's requirements and could go first. [1]: https://lore.kernel.org/linux-arm-kernel/20250304222018.615808-1-yang@xxxxxxxxxxxxxxxxxxxxxx/ Mikołaj Lenczewski (3): arm64: Add BBM Level 2 cpu feature iommu/arm: Add BBM Level 2 smmu feature arm64/mm: Elide tlbi in contpte_convert() under BBML2 .../admin-guide/kernel-parameters.txt | 3 + arch/arm64/Kconfig | 11 +++ arch/arm64/include/asm/cpucaps.h | 2 + arch/arm64/include/asm/cpufeature.h | 6 ++ arch/arm64/kernel/cpufeature.c | 76 +++++++++++++++++++ arch/arm64/kernel/pi/idreg-override.c | 2 + arch/arm64/mm/contpte.c | 3 +- arch/arm64/tools/cpucaps | 1 + .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 + drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 + drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 4 + 11 files changed, 113 insertions(+), 1 deletion(-) -- 2.48.1
