On 7/31/26 10:10 AM, [email protected] wrote:
From: Pravin M Bathija<[email protected]> The vhost-user specification (vhost-user.rst) states that no file descriptors SHOULD be passed with VHOST_USER_REM_MEM_REG. However, it also says: "For compatibility with existing incorrect implementations, the back-end MAY accept messages with one file descriptor. If a file descriptor is passed, the back-end MUST close it without using it otherwise." Some front-ends, notably libblkio, reuse the same message-building helper for both ADD_MEM_REG and REM_MEM_REG and unconditionally attach the mapping fd. The previous implementation rejected any REM_MEM_REG carrying a file descriptor with the error: expect 0 FDs for request VHOST_USER_REM_MEM_REG, received 1 This broke teardown and memory region hot-swap with these front-ends. To reproduce, run any libblkio (v1.5.0) application using the virtio-blk-vhost-user driver against a DPDK vhost back-end. The connection is dropped during cleanup or whenever a memory region is unmapped and remapped. QEMU's libvhost-user reference back-end (vu_rem_mem_reg) already tolerates zero or one fd in this message. Align DPDK's behavior with both the specification's compatibility clause and the reference implementation by accepting the message and closing any unexpected fd. Tested with: - QEMU VM bring-up with runtime add/remove memory regions via QEMU monitor - QEMU post-copy live migration between source and destination - SPDK vhost-blk with libblkio (fio libblkio engine, write + md5 verify) - libblkio alloc-mem-region and map-mem-region tests exercising ADD_MEM_REG / REM_MEM_REG / ADD_MEM_REG cycles against SPDK vhost-blk Fixes: 1d730eea6a42 ("vhost: add memory region handlers") Cc:[email protected] Signed-off-by: Pravin M Bathija<[email protected]> --- lib/vhost/vhost_user.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
Applied to next-virtio/for-next-net. Thanks, Maxime
