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PelleKrab wants to merge 9 commits into from
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[STALE] Feat: IoMmu protocol #1728

PelleKrab wants to merge 9 commits into from

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@PelleKrab
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@PelleKrab PelleKrab commented Jul 21, 2025

This PR adds the IoMmu Protocol to uefi-rs, enabling easy DMA (Direct Memory Access) for devices. This is a draft to get some initial feedback before writing uefi-rs tests. It is already working in my internal project. The main areas I would like feedback on are:

  • Mapping and DMA Buffer Types: Is this too much abstraction? Should we simplify it by requiring the developer to manually call unmap() and free_buffer()?
  • Should free_buffer_raw() and unmap_raw() be made public?
  • Repository Organization: Is the general organization within the repo appropriate?

General Implementation:

// Allocate DMA buffer
let sz = some_buffer.len();
let page_num = bytes_to_pages(sz);
let mut host_buffer = iommu.allocate_buffer(
    MemoryType::BOOT_SERVICES_DATA,
    page_num,
    EdkiiIommuAttribute::MEMORY_CACHED,
)?;

// Map buffer for DMA
let (device_addr, mapping, wrt_size) = iommu.map(
    EdkiiIommuOperation::BUS_MASTER_COMMON_BUFFER,
    &host_buffer,
    size,
)?;

// Give permissions to the specified device 
iommu.set_attribute(some_device_handle, &mapping, EdkiiIommuAccess::READ)?;

// Copy firmware to DMA buffer
let dma_buf = host_buffer.deref_mut();
if sz > wrt_size {
    return Status::BUFFER_TOO_SMALL;
}
dma_buf[..sz].copy_from_slice(&some_buffer[..sz]);

// Notify the Device and pass the `device_addr`

ref:
#1723

@nicholasbishop
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nicholasbishop commented Jul 24, 2025

Thanks for working on this :) I haven't had a chance to look at the uefi wrapper in detail yet, but overall it looks reasonable. Could you split the uefi-raw part out to a separate PR? That should be straightforward to review and merge in isolation.

@PelleKrab PelleKrab mentioned this pull request Jul 30, 2025
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nicholasbishop commented Aug 14, 2025

Is this ready for review? Currently it's marked as draft still. (No worries if that's intentional, just want to be sure you're not waiting on review.)

@PelleKrab
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PelleKrab commented Aug 14, 2025

I still need to write some test for it. I have been busy with some other things, so I'll send those over as soon as I can. Feel free to take a look if you want.

@PelleKrab
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PelleKrab commented Aug 21, 2025

@nicholasbishop I am trying to write some test for this, but I cant seem to get a protocol handle. I went into the uefi shell of the qemu vm, and the IoMmu driver image is present:

dh -p 4e939de9-d948-4b0f-88ed-e6e1ce517c1e -v
Handle dump by protocol '4E939DE9-D948-4B0F-88ED-E6E1CE517C1E'
Shell> dh -p 03c4e603-ac28-11d3-9a2d-0090273fc14d -v
Handle dump by protocol 'PXEBaseCode'
Shell> dh 28 -v
28: 3ECF0C18
ImageDevicePath(3ECF2A98)
  Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(8657015B-EA43-440D-949A-AF3BE365C0FC)
LoadedImage(3ECF20C0)
  Name..........: IoMmuDxe

So I am assuming the driver is failing to find hardware. I have tried a few different things, different EDK2 builds and followed the virtio instructions here, but nothing has worked. Ik it worked on hardware, so if you have any ideas on how to get qemu setup for IoMmu please let me know.

@phip1611
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phip1611 commented Oct 19, 2025

So I am assuming the driver is failing to find hardware. I have tried a few different things, different EDK2 builds and followed the virtio instructions here, but nothing has worked.

Thanks for trying to find a solution! Is there any update here? Have you tried to add an IOMMU to the QEMU VM? Perhaps one is needed so that the protocol will be installed one some handles (-device intel-iommu)?

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phip1611 commented Jan 25, 2026

Any update here @PelleKrab ? If not, I'm in favor of closing the PR for now.

@phip1611 phip1611 changed the title Feat: IoMmu protocol [STALE] Feat: IoMmu protocol Jan 25, 2026
@PelleKrab
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PelleKrab commented Jan 26, 2026

Any update here @PelleKrab ? If not, I'm in favor of closing the PR for now.

No significant progress yet. I've been working on this here and there. Right now, I'm building a custom OVMF image to see if that forces the xtask VM to recognize the IOMMU drivers. I'm not sure if there’s wider interest in that approach, but I'm giving it a try since no other QEMU environment configs seem to help. I'm fine with closing the issue for now, and I can reopen it if I find a solution.

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phip1611 commented Jan 26, 2026 •
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I'm fine with closing the issue for now, and I can reopen it if I find a solution.

Thanks! Good luck with your investigations. We are very happy for every contribution and feel free to reopen / open a new one as soon as you have a solution.

For good project hygiene, we aim for short-living PRs (less than 3 months best)

@phip1611 phip1611 closed this Jan 26, 2026
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3 participants

@PelleKrab @nicholasbishop @phip1611