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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?g5Jio7lG4lCaWisRBoqSkqRUjOrwDnak4yBxj6dbFGb12V17HGyuW9yqWZgv?= =?us-ascii?Q?rB1ZZO4fJBRhnkIU/yEYddCRf9MKlIhmnQ3PJhh2B5EmhZM+nObfgu3Du4c5?= =?us-ascii?Q?y5qb5wI8j4bjfz8Sri0XcJyxdMtlQjSXCe/7D8bysrKvhu5AZ6BQRqOOuGHN?= =?us-ascii?Q?O5s64e5x4aEb0THRvkveXD9L3JHJn/z8al55fzYXceRRKweohPSon12xtBvL?= =?us-ascii?Q?5kSaH0GfVHI22OoXo3XhCwZhDgv5Gknoje7CcB40RHb2P6d6DBEd/ABztZOP?= =?us-ascii?Q?CaV/Ersi7SLfQYzdZwdL7j0xC0S6h/XhGivcSpU30ghk6qe8PAuRko1DSBzY?= =?us-ascii?Q?1jmnWKvQHutK+WuNmkc0k0uyd8OsMoHDn/wjYdw3fLikgzBLJqsuZbHLqBma?= =?us-ascii?Q?jbLWX4Lfy9yedGcwmI83K8iqeta3jTCSBzToKnn4YYgc2LxCGtFC5+5uKc2C?= =?us-ascii?Q?cRNZB713IkPVX5lR8Lu/QHAOs8Uz0vlknk1N6oM7bZSivDhVKSGC1t4G4ifg?= =?us-ascii?Q?Q/o4aRySZErQQ7t1X2ALsUt+m05pg2eLu6ZIgIVJ8fc3tP9zgQ+nrHO2YbRl?= =?us-ascii?Q?0/lKGlkbVzrBu81EY1x+RBxv/xqM7myDH0xtkuP/rMLTXr+NdccmSzNBmVmY?= =?us-ascii?Q?NgWOXOuzgNb27DqZ9tvrkfvLEjqJZSyXv41kz349sx9M0cMYx5uUfXWIM/HM?= =?us-ascii?Q?yuKvL+B16G4C6fYlmP8NMpWNq/p1wd720yB3kt7NMoRdAiH/sw3AzN8JF4qi?= =?us-ascii?Q?LARg6H2+tSe/ThsqnYMZBuk/lDrFhkWnVKA9B+SonAmr+fFHyTjKqVd7uxyX?= =?us-ascii?Q?fuitIMBW1jv22FUF23dj0fXT/SRa9uTLPcEdQ8Wol8m54UVs9s3Qecb02VjS?= =?us-ascii?Q?gMN3VX7UAtdt7Li6U8g4hMsP9dDx8bPhG8FFYLRLEIgDgpdbDR2ht3U0ZYXp?= =?us-ascii?Q?j0B8Z5Z/N4vHDIrWl7DMIkUZ/6dhQPPD+hJow5Ooxqxkh1HluxBCV/2LnE7+?= =?us-ascii?Q?ckGskK6nyFVlrq+N0qAZ4xDdo7xRfKU3FP+5iisXILLzXIYGECq96ePZyOwt?= =?us-ascii?Q?ZMzn3ASSMIwNgXcLNo86fmJXb1UVAVPmDYUfqNIAnxFSgQ63SIqj+9sQew6n?= =?us-ascii?Q?/bEhUvm8IUulCsE0OelJMW1j4QRgIqP7RBgxJnPYmZNYZ+Em612tSlHl6K9u?= =?us-ascii?Q?ph5eemo7R6MyqzBlCsXIwAt7u2/MMULXBGvRwyhGqZfwN6yoexj1TxEcZkrF?= =?us-ascii?Q?6BJLfvi1wLZwG3Ro3cF7ALiHbtAZxKwDPPGeM4zhLeagCQ3MVxP/nk3AJ+G+?= =?us-ascii?Q?QVKeZOPP6NQiv9cWaQ/ECLwaK2YOXgYLa2LCe3+5yE+St4yYhqqhEsyxTJfs?= =?us-ascii?Q?qa5Hqei3C4KvEhU4tbkxdODtyenGEsxcom4Vp+q2VJh2YuwSL0k/hgNkBNP6?= =?us-ascii?Q?N3dhL+U+y5cCvZHV/n4Bt+KR4KYIMV1x6qYx3PwYDTfUm+rH8wJfVfdt3x9w?= =?us-ascii?Q?DVGh1sgnU68Go7XbziXSTXrwTqSA7qOVvHe+isyxBNS21HFn2Fd7kQH8QMl8?= =?us-ascii?Q?Z41tTcj9lxCTXBz8JTyYMmiFmSlyLckMdxxWeqZl8VsHewN8uXmBqK5Zvyuu?= =?us-ascii?Q?fuTYPYAt080L1Dat9/ajbuX0X5TQBQJGuE7dUcIyNnkiYJcvKsNNg3jUUZfq?= =?us-ascii?Q?apM7sCqIQ69KRaFz2BikAm/D5r71CWCN5EOe6wfKfxBN9Qojbaiayqa/BdRQ?= =?us-ascii?Q?llbM4yAozg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 00933dab-da08-4b75-ce65-08deb2cde28f X-MS-Exchange-CrossTenant-AuthSource: LV3PR12MB9411.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 May 2026 22:04:07.3422 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: szhznnqFLz5dT5jxIsCSIdb+pYKvCqmGmIEPHlyRmLGd9DCJbmKnZTFJzP7J6s7diLhotiU+WUck5wLNGVWt0g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7751 The submitted driver waits at most 1 ms (100 * 10 us) for the last RX descriptor to be written back. QEMU's emulated loopback is synchronous: by the time igb_memcpy_wait() runs, the receive descriptors are already written back. Real 82576 hardware processes the descriptor ring at line rate. max_memcpy_size is (RING_SIZE - 1) * IGB_MAX_CHUNK_SIZE, approximately 4 MB, split into 4095 1 KB frames. At 1 Gb/s line rate (~125 MB/s), 4 MB takes ~32 ms on the wire, plus per-frame preamble, SFD, inter-frame gap and FCS overhead (~3%) and descriptor fetch/writeback latency. The 1 ms cap times out long before any valid transfer can complete. Wait up to ~200 ms (200 iterations * 1 ms) for descriptor writeback before returning -ETIMEDOUT. ~6x the line-rate floor leaves comfortable headroom for host scheduling jitter and slower PCIe paths, while still bounding the intentional invalid-DMA tests (mix_and_match) so they recover quickly on real faults. Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Alex Williamson --- .../testing/selftests/vfio/lib/drivers/igb/igb.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/vfio/lib/drivers/igb/igb.c b/tools/testing/selftests/vfio/lib/drivers/igb/igb.c index d44a08a36171..2297382d7c26 100644 --- a/tools/testing/selftests/vfio/lib/drivers/igb/igb.c +++ b/tools/testing/selftests/vfio/lib/drivers/igb/igb.c @@ -422,11 +422,22 @@ static int igb_memcpy_wait(struct vfio_pci_device *device) prev_tail = (igb->rx_tail + RING_SIZE - 1) % RING_SIZE; rx = &igb->rx_ring[prev_tail]; - retries = 100; + /* + * Real 82576 hardware processes the descriptor ring at line rate. + * max_memcpy_size = (RING_SIZE - 1) * IGB_MAX_CHUNK_SIZE ~= 4 MB, + * split into 4095 1 KB frames. At 1 Gb/s (~125 MB/s) the worst + * valid memcpy takes ~32 ms on the wire, plus per-frame preamble, + * SFD, IFG and FCS overhead (~3%) and descriptor fetch/writeback + * latency. Wait up to ~200 ms before declaring the device hung; + * ~6x the line-rate floor leaves comfortable headroom for host + * scheduling jitter while keeping the intentional invalid-DMA + * tests bounded. + */ + retries = 200; while (retries-- > 0) { if (rx->wb.status_error & 1) break; - usleep(10); + usleep(1000); } igb_irq_clear(igb); -- 2.51.0