nvme_driver: support multi-page allocations for queues

[mattkur]

The vast majority of this work was done by @chris-oo , many thanks to him!

The outstanding queue depth from the nvme driver can be limited by the number of entries in the IO submission queue. Prior to this change, OpenHCL's nvme driver supported 1 page worth of submission queue entries. After this change, the nvme driver will support as many queue entries as the device supports.

Contiguous allocations are likely, but not strictly guaranteed. This code opts to allow forward progress by falling back to one page allocations. This is testable (and has been validated manually and with some of the existing CI tests) by not configuring a private pool.

There are some other design tradeoffs, which are noted as comments in the change.

[Copilot]

Pull Request Overview

This PR enhances the NVMe driver to support multi-page queue allocations, enabling higher queue depths and better I/O performance. The driver now attempts to allocate multi-page contiguous memory for queues while maintaining backward compatibility by falling back to single-page allocations when contiguous memory is unavailable.

Key changes:

• Expanded queue size support from single-page to multi-page allocations
• Added fallback mechanism for non-contiguous memory scenarios
• Enhanced DMA allocation with private pool fallback support

Reviewed Changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
vm/devices/storage/disk_nvme/nvme_driver/src/queue_pair.rs	Core queue pair implementation with multi-page support and contiguous memory detection
vm/devices/storage/disk_nvme/nvme_driver/src/driver.rs	Driver initialization updates to handle variable queue sizes
vm/devices/storage/disk_nvme/nvme_driver/src/queues.rs	Queue structure updates with debug logging and completion read optimization
vm/devices/user_driver/src/memory.rs	Added contiguous PFN detection utility method
openhcl/openhcl_dma_manager/src/lib.rs	Enhanced DMA manager with private pool fallback allocation strategy
vmm_tests/vmm_tests/tests/tests/x86_64/openhcl_linux_direct.rs	Test updates to enable VTL2 GPA pool and add cached I/O testing
openhcl/openhcl_boot/src/main.rs	Boot parameter handling for NVMe keep-alive control
openhcl/openhcl_boot/src/cmdline.rs	Command line parsing for NVMe keep-alive disable option
openhcl/openhcl_dma_manager/Cargo.toml	Added tracing dependency for logging support
vm/devices/user_driver/src/lib.rs	API documentation updates for DMA allocation

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