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

[Vipin Sharma <vipinsh@google.com>]

On Tue, Jul 14, 2026 at 03:37:40PM +0000, sashiko-bot@kernel.org wrote:
> 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().
> --
> 
> --- 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?
> 

It is an issue, even though we are not verifying the copied data yet.

I will fix it in the next version.

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