On Tue, Aug 06, 2024 at 07:11:53PM -0700, Nicolin Chen wrote:

From: Nate Watterson <redacted>

NVIDIA's Tegra241 Soc has a CMDQ-Virtualization (CMDQV) hardware, extending
the standard ARM SMMU v3 IP to support multiple VCMDQs with virtualization
capabilities. In terms of command queue, they are very like a standard SMMU
CMDQ (or ECMDQs), but only support CS_NONE in the CS field of CMD_SYNC.

Add a new tegra241-cmdqv driver, and insert its structure pointer into the
existing arm_smmu_device, and then add related function calls in the SMMUv3
driver to interact with the CMDQV driver.

In the CMDQV driver, add a minimal part for the in-kernel support: reserve
VINTF0 for in-kernel use, and assign some of the VCMDQs to the VINTF0, and
select one VCMDQ based on the current CPU ID to execute supported commands.
This multi-queue design for in-kernel use gives some limited improvements:
up to 20% reduction of invalidation time was measured by a multi-threaded
DMA unmap benchmark, compared to a single queue.

The other part of the CMDQV driver will be user-space support that gives a
hypervisor running on the host OS to talk to the driver for virtualization
use cases, allowing VMs to use VCMDQs without trappings, i.e. no VM Exits.
This is designed based on IOMMUFD, and its RFC series is also under review.
It will provide a guest OS a bigger improvement: 70% to 90% reductions of
TLB invalidation time were measured by DMA unmap tests running in a guest,
compared to nested SMMU CMDQ (with trappings).

As the initial version, the CMDQV driver only supports ACPI configurations.

Signed-off-by: Nate Watterson <redacted>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Co-developed-by: Nicolin Chen <redacted>
Signed-off-by: Nicolin Chen <redacted>
---
 MAINTAINERS                                   |   1 +
 drivers/iommu/Kconfig                         |  11 +
 drivers/iommu/arm/arm-smmu-v3/Makefile        |   1 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |   9 +
 .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c    | 868 ++++++++++++++++++
 5 files changed, 890 insertions(+)
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c

[...]

+struct arm_smmu_device *
+tegra241_cmdqv_acpi_dsdt_probe(struct arm_smmu_device *smmu,
+			       struct acpi_iort_node *node)
+{
+	struct resource *res;
+	int irq;
+
+	/* Keep the pointer smmu intact if !res */
+	res = tegra241_cmdqv_find_acpi_resource(smmu, node, &irq);
+	if (!res)
+		return smmu;

Given that this probing code will end up running on non-tegra hardware
when CONFIG_TEGRA241_CMDQV is enabled, please can you move the common
part into the main driver?

Will