Michael S. Tsirkin d085eb8ce7 vhost: disable for OABI ... vhost is currently broken on the some ARM configs. The reason is that the ring element addresses are passed between components with different alignments assumptions. Thus, if guest selects a pointer and host then gets and dereferences it, then alignment assumed by the host's compiler might be greater than the actual alignment of the pointer. compiler on the host from assuming pointer is aligned. This actually triggers on ARM with -mabi=apcs-gnu - which is a deprecated configuration. With this OABI, compiler assumes that all structures are 4 byte aligned - which is stronger than virtio guarantees for available and used rings, which are merely 2 bytes. Thus a guest without -mabi=apcs-gnu running on top of host with -mabi=apcs-gnu will be broken. The correct fix is to force alignment of structures - however that is an intrusive fix that's best deferred until the next release. We didn't previously support such ancient systems at all - this surfaced after vdpa support prompted removing dependency of vhost on VIRTULIZATION. So for now, let's just add something along the lines of depends on !ARM || AEABI to the virtio Kconfig declaration, and add a comment that it has to do with struct member alignment. Note: we can't make VHOST and VHOST_RING themselves have a dependency since these are selected. Add a new symbol for that. We should be able to drop this dependency down the road. Fixes: 20c384f1ea ("vhost: refine vhost and vringh kconfig") Suggested-by: Ard Biesheuvel <ardb@kernel.org> Suggested-by: Richard Earnshaw <Richard.Earnshaw@arm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>		2020-04-20 10:19:22 -04:00
..
ifcvf	vdpa: allow a 32 bit vq alignment	2020-04-17 06:05:30 -04:00
vdpa_sim	vdpa: allow a 32 bit vq alignment	2020-04-17 06:05:30 -04:00
Kconfig	vhost: disable for OABI	2020-04-20 10:19:22 -04:00
Makefile
vdpa.c	vdpa: fix comment of vdpa_register_device()	2020-04-17 06:05:30 -04:00