Re: [PATCH v6 0/7] soc: ti: Add and use PVU on K3-AM65 for DMA isolation

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Sep 09, 2024 at 07:03:53PM +0200, Jan Kiszka wrote:
> Changes in v6:
>  - make restricted DMA memory-region available to all pci-keystone
>    devices, moving property to unconditional section (patch 2)
> 
> Changes in v5:
>  - resolve review comments on pci-host bindings
>  - reduce DMA memory regions to 1 - swiotlb does not support more
>  - move activation into overlay (controlled via firmware)
>  - use ks_init_vmap helper instead of loop in
>    rework ks_init_restricted_dma
>  - add more comments to pci-keystone
>  - use 2 chained TLBs of PVU to support maximum of swiotlb (320 MB)
> 
> Changes in v4:
>  - reorder patch queue, moving all DTS changes to the back
>  - limit activation to IOT2050 Advanced variants
>  - move DMA pool to allow firmware-based expansion it up to 512M
> 
> Changes in v3:
>  - fix ti,am654-pvu.yaml according to review comments
>  - address review comments on ti,am65-pci-host.yaml
>  - differentiate between different compatibles in ti,am65-pci-host.yaml
>  - move pvu nodes to k3-am65-main.dtsi
>  - reorder patch series, pulling bindings and generic DT bits to the front
> 
> Changes in v2:
>  - fix dt_bindings_check issues (patch 1)
>  - address first review comments (patch 2)
>  - extend ti,am65-pci-host bindings for PVU (new patch 3)
> 
> Only few of the K3 SoCs have an IOMMU and, thus, can isolate the system
> against DMA-based attacks of external PCI devices. The AM65 is without
> an IOMMU, but it comes with something close to it: the Peripheral
> Virtualization Unit (PVU).
> 
> The PVU was originally designed to establish static compartments via a
> hypervisor, isolate those DMA-wise against each other and the host and
> even allow remapping of guest-physical addresses. But it only provides
> a static translation region, not page-granular mappings. Thus, it cannot
> be handled transparently like an IOMMU.
> 
> Now, to use the PVU for the purpose of isolated PCI devices from the
> Linux host, this series takes a different approach. It defines a
> restricted-dma-pool for the PCI host, using swiotlb to map all DMA
> buffers from a static memory carve-out. And to enforce that the devices
> actually follow this, a special PVU soc driver is introduced. The driver
> permits access to the GIC ITS and otherwise waits for other drivers that
> detect devices with constrained DMA to register pools with the PVU.
> 
> For the AM65, the first (and possibly only) driver where this is
> introduced is the pci-keystone host controller. Finally, this series
> provides a DT overlay for the IOT2050 Advanced devices (all have
> MiniPCIe or M.2 extension slots) to make use of this protection scheme.
> Application of this overlay will be handled by firmware.
> 
> Due to the cross-cutting nature of these changes, multiple subsystems
> are affected. However, I wanted to present the whole thing in one series
> to allow everyone to review with the complete picture in hands. If
> preferred, I can also split the series up, of course.

I'm not sure where this ended up.

The pci-keystone.c patch looks OK to me, and I don't see any comments
from the PCI folks who normally take care of host controller drivers.

I guess it depends on the soc PVU driver, so I'll ack the keystone
part and whoever takes the soc part can include it.

> CC: Bjorn Helgaas <bhelgaas@google.com>
> CC: "Krzysztof Wilczyński" <kw@linux.com>
> CC: linux-pci@vger.kernel.org
> CC: Lorenzo Pieralisi <lpieralisi@kernel.org>
> 
> Jan Kiszka (7):
>   dt-bindings: soc: ti: Add AM65 peripheral virtualization unit
>   dt-bindings: PCI: ti,am65: Extend for use with PVU
>   soc: ti: Add IOMMU-like PVU driver
>   PCI: keystone: Add support for PVU-based DMA isolation on AM654
>   arm64: dts: ti: k3-am65-main: Add PVU nodes
>   arm64: dts: ti: k3-am65-main: Add VMAP registers to PCI root complexes
>   arm64: dts: ti: iot2050: Add overlay for DMA isolation for devices
>     behind PCI RC
> 
>  .../bindings/pci/ti,am65-pci-host.yaml        |  28 +-
>  .../bindings/soc/ti/ti,am654-pvu.yaml         |  51 ++
>  arch/arm64/boot/dts/ti/Makefile               |   5 +
>  arch/arm64/boot/dts/ti/k3-am65-main.dtsi      |  38 +-
>  ...am6548-iot2050-advanced-dma-isolation.dtso |  33 ++
>  drivers/pci/controller/dwc/pci-keystone.c     | 108 ++++
>  drivers/soc/ti/Kconfig                        |   4 +
>  drivers/soc/ti/Makefile                       |   1 +
>  drivers/soc/ti/ti-pvu.c                       | 500 ++++++++++++++++++
>  include/linux/ti-pvu.h                        |  16 +
>  10 files changed, 777 insertions(+), 7 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/soc/ti/ti,am654-pvu.yaml
>  create mode 100644 arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced-dma-isolation.dtso
>  create mode 100644 drivers/soc/ti/ti-pvu.c
>  create mode 100644 include/linux/ti-pvu.h
> 
> -- 
> 2.43.0
>