scsidisk: Support WRITE_ATOMIC(16) SCSI command in NVMe-backed storage #1518
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| .unwrap_or(0), | ||
| "transfer length OR non-zero atomic boundary not multiple of atomic transfer length granularity" | ||
| ); | ||
| return Err(ScsiError::IllegalRequest(AdditionalSenseCode::INVALID_CDB)); |
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I recognize that you are still mulling over the validation strategy here, but this type of thing is useful to include as a unit test (basic packet parsing & protocol validations).
| let cdb = scsi::Cdb16Atomic::read_from_prefix(&request.cdb[..]) | ||
| .unwrap() | ||
| .0; // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759) | ||
| let len = cdb.transfer_blocks.get() as u64; |
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len in Rust usually refers to a byte length. Consider block_count or sector_count something.
| if len as u32 | ||
| % self | ||
| .scsi_parameters | ||
| .atomic_transfer_length_granularity |
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Is it possible to require the granularity to be a power of 2? If so, avoid %--store a shift and use shift/mask operations.
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This would be dependent upon the underlying storage. I don't think we can guarantee such a thing.
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So this changes the What that means is that this will be impractical to implement for anything other than our NVMe driver, since other interfaces require opt in (e.g., SCSI, Linux block layer). This may be artificially limiting. I think we should consider adding some kind of |
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There's zero way to test any of this currently. I think you need to implement this in the NVMe emulator and something like RAM disk (which will also require extending this through the layered disk infra... which shouldn't be too bad). |
This PR adds support for the WRITE_ATOMIC(16) SCSI command in the SCSI device OpenHCL presents to guests. NVMe devices support atomic writes implicitly, as long as the bounds of the operation are kept within specific bounds specified in the NVMe identify information.
#947