kernel/linux.git/drivers/virtio/virtio.c, branch v4.14.286

virtio: acknowledge all features before access

2022-03-16T11:57:09+00:00

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 404123c2db79 ("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 Cc: stable@vger.kernel.org Fixes: 404123c2db79 ("virtio: allow drivers to validate features") Fixes: 2f9a174f918e ("virtio: write back F_VERSION_1 before validate") Cc: "Halil Pasic" Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman

virtio: unexport virtio_finalize_features

2022-03-16T11:57:09+00:00

commit 838d6d3461db0fdbf33fc5f8a69c27b50b4a46da upstream. virtio_finalize_features is only used internally within virtio. No reason to export it. Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck Acked-by: Jason Wang Signed-off-by: Greg Kroah-Hartman

virtio: write back F_VERSION_1 before validate

2021-10-20T08:42:04+00:00

commit 2f9a174f918e29608564c7a4e8329893ab604fb4 upstream. The virtio specification virtio-v1.1-cs01 states: "Transitional devices MUST detect Legacy drivers by detecting that VIRTIO_F_VERSION_1 has not been acknowledged by the driver." This is exactly what QEMU as of 6.1 has done relying solely on VIRTIO_F_VERSION_1 for detecting that. However, the specification also says: "... the driver MAY read (but MUST NOT write) the device-specific configuration fields to check that it can support the device ..." before setting FEATURES_OK. In that case, any transitional device relying solely on VIRTIO_F_VERSION_1 for detecting legacy drivers will return data in legacy format. In particular, this implies that it is in big endian format for big endian guests. This naturally confuses the driver which expects little endian in the modern mode. It is probably a good idea to amend the spec to clarify that VIRTIO_F_VERSION_1 can only be relied on after the feature negotiation is complete. Before validate callback existed, config space was only read after FEATURES_OK. However, we already have two regressions, so let's address this here as well. The regressions affect the VIRTIO_NET_F_MTU feature of virtio-net and the VIRTIO_BLK_F_BLK_SIZE feature of virtio-blk for BE guests when virtio 1.0 is used on both sides. The latter renders virtio-blk unusable with DASD backing, because things simply don't work with the default. See Fixes tags for relevant commits. For QEMU, we can work around the issue by writing out the feature bits with VIRTIO_F_VERSION_1 bit set. We (ab)use the finalize_features config op for this. This isn't enough to address all vhost devices since these do not get the features until FEATURES_OK, however it looks like the affected devices actually never handled the endianness for legacy mode correctly, so at least that's not a regression. No devices except virtio net and virtio blk seem to be affected. Long term the right thing to do is to fix the hypervisors. Cc: #v4.11 Signed-off-by: Halil Pasic Fixes: 82e89ea077b9 ("virtio-blk: Add validation for block size in config space") Fixes: fe36cbe0671e ("virtio_net: clear MTU when out of range") Reported-by: markver@us.ibm.com Reviewed-by: Cornelia Huck Link: https://lore.kernel.org/r/20211011053921.1198936-1-pasic@linux.ibm.com Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman

virtio: release virtio index when fail to device_register

2017-12-14T08:52:48+00:00

commit e60ea67bb60459b95a50a156296041a13e0e380e upstream. index can be reused by other virtio device. Signed-off-by: weiping zhang Reviewed-by: Cornelia Huck Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman

virtio: allow drivers to validate features

2017-04-07T13:38:59+00:00

Some drivers can't support all features in all configurations. At the moment we blindly set FEATURES_OK and later FAILED. Support this better by adding a callback drivers can use to do some early checks. Signed-off-by: Michael S. Tsirkin

virtio_net: refactor freeze/restore logic into virtnet reset logic

2017-02-07T15:05:12+00:00

For XDP we will need to reset the queues to allow for buffer headroom to be configured. In order to do this we need to essentially run the freeze()/restore() code path. Unfortunately the locking requirements between the freeze/restore and reset paths are different however so we can not simply reuse the code. This patch refactors the code path and adds a reset helper routine. Signed-off-by: John Fastabend Acked-by: Jason Wang Signed-off-by: David S. Miller

virtio: fix memory leak of virtio ida cache layers

2015-12-07T15:28:01+00:00

The virtio core uses a static ida named virtio_index_ida for assigning index numbers to virtio devices during registration. The ida core may allocate some internal idr cache layers and an ida bitmap upon any ida allocation, and all these layers are truely freed only upon the ida destruction. The virtio_index_ida is not destroyed at present, leading to a memory leak when using the virtio core as a module and atleast one virtio device is registered and unregistered. Fix this by invoking ida_destroy() in the virtio core module exit. Cc: stable@vger.kernel.org Signed-off-by: Suman Anna Signed-off-by: Michael S. Tsirkin

virtio: drop virtio_device_is_legacy_only

2015-04-15T03:11:14+00:00

virtio_device_is_legacy_only is now unused, drop it from core. Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck Signed-off-by: Rusty Russell

virtio: balloon might not be a legacy device

2015-04-15T03:11:11+00:00

We added transitional device support to balloon driver, so we don't need to black-list it in core anymore. Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck Signed-off-by: Rusty Russell

virtio: don't set VIRTIO_CONFIG_S_DRIVER_OK twice.

2015-02-17T05:49:29+00:00

I noticed this with the console device. It's not *wrong*, just a bit weird. Signed-off-by: Rusty Russell