Re: [PATCH v9 0/5] iommu: Support mappings/reservations in reserved-memory regions

Thierry Reding
2022-10-07T12:52:01Z

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On Fri, Sep 23, 2022 at 02:35:52PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
>
> Hi,
>
> This version has several fixes over the previous v8, which can be found
> here:
>
> https://lore.kernel.org/all/20220905170833.396892-1-thierry.reding@gmail.com/
>
> An example is included in the DT bindings, but here is an extract of
> what I've used to test this:
>
> reserved-memory {
> #address-cells = <2>;
> #size-cells = <2>;
> ranges;
>
> /*
> * Creates an identity mapping for the framebuffer that
> * the firmware has setup to scan out a bootsplash from.
> */
> fb: framebuffer@92cb2000 {
> reg = <0x0 0x92cb2000 0x0 0x00800000>;
> iommu-addresses = <&dc0 0x0 0x92cb2000 0x0 0x00800000>;
> };
>
> /*
> * Creates a reservation in the IOVA space to prevent
> * any buffers from being mapped to that region. Note
> * that on Tegra the range is actually quite different
> * from this, but it would conflict with the display
> * driver that I tested this against, so this is just
> * a dummy region for testing.
> */
> adsp: reservation-adsp {
> iommu-addresses = <&dc0 0x0 0x90000000 0x0 0x00010000>;
> };
> };
>
> host1x@50000000 {
> dc@54200000 {
> memory-region = <&fb>, <&adsp>;
> };
> };
>
> This is abbreviated a little to focus on the essentials. Note also that
> the ADSP reservation is not actually used on this device and the driver
> for this doesn't exist yet, but I wanted to include this variant for
> testing, because we'll want to use these bindings for the reservation
> use-case as well at some point.
>
> I've also been able to make use of this binding and the IOMMU code in
> conjunction with the simple-framebuffer driver to hand over a display
> configuration set up by UEFI to the Linux kernel.
>
> Janne has confirmed[0] this to be suitable for indirect mappings as
> well, though these patches don't implement that feature yet. Potential
> extensions to this have been discussed but are not yet included at this
> time to not further complicate things.
>
> Thierry
>
> [0]: https://lore.kernel.org/all/20220909144504.GA4024@jannau.net/
>
> Navneet Kumar (1):
> iommu/tegra-smmu: Support managed domains
>
> Thierry Reding (4):
> dt-bindings: reserved-memory: Document iommu-addresses
> iommu: Implement of_iommu_get_resv_regions()
> iommu: dma: Use of_iommu_get_resv_regions()
> iommu/tegra-smmu: Add support for reserved regions
>
> .../reserved-memory/reserved-memory.yaml | 70 ++++++++++++
> drivers/iommu/dma-iommu.c | 3 +
> drivers/iommu/of_iommu.c | 104 ++++++++++++++++++
> drivers/iommu/tegra-smmu.c | 86 ++++++++++++---
> include/linux/of_iommu.h | 8 ++
> 5 files changed, 254 insertions(+), 17 deletions(-)

Joerg, if there are no further concerns on this, can you pick this up
once v6.1-rc1 is released?

Thanks,
Thierry

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