iSCSI hook and IOMMU

[mcb30]

(2018-11-19 14:38)parthy Wrote:  I've observed issues when using iSCSI sanhook in conjunction with the IOMMU. When the loaded kernel enables the IOMMU, the traffic caused by the iSCSI hook eventually causes DMA faults, because the NIC uses DMA regions that are not registered anywhere.

Since iPXE acts like a kind of firmware in this case, shouldn't it register the NIC and corresponding memory regions in the RMRRs?

There is no protocol by which iPXE can negotiate IOMMU registrations with the host OS. What should happen is that the kernel takes over ownership of all hardware, including the IOMMU and the NIC, and ceases to use the INT13 API.

There is some logic within iPXE to quiesce the hardware (i.e. stop DMA) at the points that iPXE expects the OS to potentially take ownership. This is currently implemented only for Hyper-V, but could be extended for other NICs.

Michael