Re: [PATCH v5 20/20] vfio: selftests: Add continuous DMA to vfio_pci_liveupdate_kexec_test

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Partial initialization of DMA buffers in dma_memcpy_start().
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--- Patch [20]: [PATCH v5 20/20] vfio: selftests: Add continuous DMA to vfio_pci_liveupdate_kexec_test ---
Note: Due to system recitation restrictions, this report does not use the standard inline diff quoting format. The findings are instead summarized below without quoting the original patch code.

commit 123ec8cfeb386e8660107c771eabe7ddc5cba029
Author: David Matlack <dmatlack@google.com>

vfio: selftests: Add continuous DMA to vfio_pci_liveupdate_kexec_test

This commit adds a long-running DMA memcpy operation to the VFIO PCI live
update kexec test. It ensures that active device DMAs during a live update do
not cause system instability, even though the DMAs are currently expected to
be dropped.

[Severity: Medium]
In tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c, looking at
the dma_memcpy_start() function, the buffer initialization seems incomplete.

The code calculates the transfer size and sets the destination pointer, but
then calls memset() on the source and destination buffers using 'size / 2'
instead of 'size'. Immediately after, vfio_pci_driver_memcpy_start() is
kicked off using the full 'size'.

Does this code unintentionally leave the second half of the DMA buffers
uninitialized? While the test does not currently verify the transferred data
since iommufd preservation is unsupported, will this partial initialization
cause false positives or negatives once the test is expanded to validate the
completed DMA operations?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260714151505.3466855-1-vipinsh@google.com?part=20