Michael S. Tsirkin 573a3228ca virtio: acknowledge all features before access ... commit 4fa59ede95195f267101a1b8916992cf3f245cdb upstream. The feature negotiation was designed in a way that makes it possible for devices to know which config fields will be accessed by drivers. This is broken since commit 404123c2db ("virtio: allow drivers to validate features") with fallout in at least block and net. We have a partial work-around in commit 2f9a174f918e ("virtio: write back F_VERSION_1 before validate") which at least lets devices find out which format should config space have, but this is a partial fix: guests should not access config space without acknowledging features since otherwise we'll never be able to change the config space format. To fix, split finalize_features from virtio_finalize_features and call finalize_features with all feature bits before validation, and then - if validation changed any bits - once again after. Since virtio_finalize_features no longer writes out features rename it to virtio_features_ok - since that is what it does: checks that features are ok with the device. As a side effect, this also reduces the amount of hypervisor accesses - we now only acknowledge features once unless we are clearing any features when validating (which is uncommon). IRC I think that this was more or less always the intent in the spec but unfortunately the way the spec is worded does not say this explicitly, I plan to address this at the spec level, too. Acked-by: Jason Wang <jasowang@redhat.com> Cc: stable@vger.kernel.org Fixes: 404123c2db ("virtio: allow drivers to validate features") Fixes: 2f9a174f918e ("virtio: write back F_VERSION_1 before validate") Cc: "Halil Pasic" <pasic@linux.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-03-16 14:16:02 +01:00
..
Kconfig
Makefile
virtio_balloon.c
virtio_dma_buf.c
virtio_input.c
virtio_mem.c
virtio_mmio.c
virtio_pci_common.c
virtio_pci_common.h
virtio_pci_legacy.c
virtio_pci_modern.c
virtio_ring.c	virtio_ring: mark ring unused on error	2022-01-27 10:54:33 +01:00
virtio_vdpa.c
virtio.c	virtio: acknowledge all features before access	2022-03-16 14:16:02 +01:00