Re: [PATCH v4 00/10] vhost-user: Preparatory series for multiple iovec entries per virtqueue element

On Wed, 20 May 2026 17:34:45 +0200 Stefano Brivio wrote:

On Wed, 13 May 2026 13:52:08 +0200 Laurent Vivier wrote:

...

Currently, the vhost-user path assumes each virtqueue element contains exactly one iovec entry covering the entire frame. This assumption breaks as some virtio-net drivers (notably iPXE) provide descriptors where the vnet header and the frame payload are in separate buffers, resulting in two iovec entries per virtqueue element.

This series refactors the vhost-user data path so that frame lengths, header sizes, and padding are tracked and passed explicitly rather than being derived from iovec sizes. This decoupling is a prerequisite for correctly handling padding of multi-buffer frames.

Sorry to bring (likely) bad news, but this series seems to introduce a regression: I got the migration/rampstream_in tests fail twice in a row, which I've never saw happening (I think I saw a single failure a long time ago when the machine had a high CPU load, but nothing else).

I'm currently bisecting and the bisect seems to point towards the end of the series (probably 10/10), but I haven't finished yet. I'll keep you posted. I haven't spotted anything that might cause issues there.

Yeah, that's the one :( $ git bisect bad db798fc60f4c5869cb53168354e068fb4dabd91a is the first bad commit commit db798fc60f4c5869cb53168354e068fb4dabd91a Author: Laurent Vivier Date: Wed May 13 13:52:18 2026 +0200 vhost-user: Centralise Ethernet frame padding in vu_collect() and vu_pad() The "TCP/IPv4: sequence check, ramps, inbound" test in rampstream_in gets stuck, once the source is done with the migration, and passt on the destination just printed: Accepted TCP_REPAIR helper, PID 13 accepted connection from PID 16 I'll get captures and logs next. It seems to fail most of the times, I had two failures in a row again. -- Stefano