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Sashiko AI review found 1 potential is= sue(s) to consider: > > - [Medium] Test flakiness due to fixed heuristic delay instead of polli= ng on EAGAIN during VFIO_DEVICE_RESET > > -- > > > > --- Patch [5]: [PATCH v5 5/5] vfio: selftests: igb: Recover after DMA-r= ead faults --- > > commit a631c99ce1be37dbbdda0314b730b2c6bd947b50 > > Author: Alex Williamson > > > > vfio: selftests: igb: Recover after DMA-read faults > > > > This commit adds recovery logic to the igb selftest when an intentional= DMA > > read fault causes the device to hang. It introduces a reset and re-init > > sequence using VFIO_DEVICE_RESET, including a 10ms delay to allow kerne= l > > error handlers to release the device lock. > > =20 > > > diff --git a/tools/testing/selftests/vfio/lib/drivers/igb/igb.c b/too= ls/testing/selftests/vfio/lib/drivers/igb/igb.c > > > --- a/tools/testing/selftests/vfio/lib/drivers/igb/igb.c > > > +++ b/tools/testing/selftests/vfio/lib/drivers/igb/igb.c =20 > > > > [ ... ] > > =20 > > > @@ -500,7 +522,28 @@ static int igb_memcpy_wait(struct vfio_pci_devic= e *device) > > > > > > igb_irq_enable(igb); > > > > > > - return (status & 1) ? 0 : -ETIMEDOUT; > > > + if (status & 1) > > > + return 0; > > > + > > > + /* > > > + * The descriptor never completed. On real 82576 hardware this > > > + * typically follows a DMA-read fault from one of the intention= al > > > + * unmapped-IOVA tests; the fault leaves the descriptor engine > > > + * unable to service subsequent valid descriptors. CTRL.RST al= one > > > + * reinitializes the queue registers but leaves the engine wedg= ed > > > + * for the current process, so a broader VFIO_DEVICE_RESET (FLR= ) > > > + * is required. > > > + * > > > + * Delay before requesting reset so PCIe/IOMMU/AER error handli= ng > > > + * triggered by the just-observed DMA fault can release the dev= ice > > > + * lock VFIO_DEVICE_RESET contends for. The 10 ms value is > > > + * heuristic. The current memcpy still fails with -ETIMEDOUT; > > > + * recovery only ensures the next memcpy starts from a usable s= tate. > > > + */ > > > + usleep(10000); > > > + igb_error_reset_and_reinit(device); =20 > > > > [Severity: Medium] > > Will this fixed heuristic delay cause test flakiness under heavy load? > > > > If the kernel's PCIe/IOMMU/AER error handling takes longer than 10ms to > > complete (for example, when KASAN or other heavy debugging options are > > enabled), the device lock might still be held. > > > > Looking at the kernel side in drivers/vfio/pci/vfio_pci_core.c: > > vfio_pci_ioctl_reset(), lock contention causes pci_try_reset_function()= to > > return -EAGAIN: > > > > ret =3D pci_try_reset_function(vdev->pdev); > > if (__vfio_pci_memory_enabled(vdev)) > > vfio_pci_dma_buf_move(vdev, false); > > up_write(&vdev->memory_lock); > > > > return ret; > > > > Since igb_error_reset_and_reinit() calls vfio_pci_device_reset(), which > > asserts that the ioctl returns 0, would this lock contention cause an > > immediate test suite failure? > > > > Should this code explicitly poll for -EAGAIN from the ioctl instead of > > relying entirely on a fixed sleep? > > =20 > > > + return -ETIMEDOUT; =20 >=20 > Alex, I'm guessing 10ms is what worked for you when testing with the > physical hardware? If it's working fine, I don't think it needs to be > changed. Yes, the delay was found empirically and indeed we could make this more robust if we retried on -EAGAIN. I'd be in favor of doing that as a follow-up. Thanks, Alex