swiotlb: CONFIG_SWIOTLB_DYNAMIC=y. Enable dynamic allocation of DMA bounce buffers.

[ZvmNNoHlQjYb]

Same-request check

Yes

Linux Distribution affected

All

Feature description

See zen-kernel/zen-kernel#393

For sw iommu CONFIG_SWIOTLB_DYNAMIC=y is an advantageous config for nearly all users.
SWIOTLB is used with generic (fallback) / Intel VT-d. It’s just AMD going HW accelerated and not using swiotlb.

See the related issue in the Zen Kernel for further IOMMU recommendations

(strict IOMMU by default instead lazy, turning AMD-Vi (amd_iommu) completely off since it’s causing page faults and restricts hardware compatibility). SW IOMMU should be the default. This means, Intel VT-d config parameters may also be kept unchanged. Intel just chose the existing solution (SW IOMMU) and extended.

IMO, the fw provided with the delivered UEFI (virtualization, IOMMU, etc.) is just basic for first setup and boot. Rely on SW implementation (Kernel, runtime, userspace) instead everytime you can.

The system runs much more stable and feels more independent.

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[ZvmNNoHlQjYb]

It is an enhancement. Definitely. Let’s not start talking about turning amd_iommu off, for now.

But CONFIG_SWIOTLB_DYNAMIC must be enabled. At least for the Intel users.

[ZvmNNoHlQjYb]

Thank me later. Ran into all possible issues. From page faults to full bounce buffers with an unresponsive wifi device. The default config is completely BS.