[RFC PATCH v3 7/8] vhost: annotate IOTLB locks

[Maxime Coquelin]

On 4/11/22 13:00, David Marchand wrote:
> This change simply annotates existing paths of the code leading to
> manipulations of the IOTLB r/w locks.
> 
> clang does not support conditionally held locks, so always take iotlb
> locks regardless of VIRTIO_F_IOMMU_PLATFORM feature.
> 
> vdpa and vhost_crypto code are annotated though they end up not taking
> a IOTLB lock and have been marked with a FIXME.
> 
> Signed-off-by: David Marchand <david.marchand at redhat.com>
> ---
>   lib/vhost/iotlb.h        |  8 +++++++
>   lib/vhost/vdpa.c         |  1 +
>   lib/vhost/vhost.c        | 11 +++++----
>   lib/vhost/vhost.h        | 22 +++++++++++++-----
>   lib/vhost/vhost_crypto.c |  7 ++++++
>   lib/vhost/virtio_net.c   | 49 ++++++++++++++++++++++++++++++----------
>   6 files changed, 75 insertions(+), 23 deletions(-)
> 


I agree with the change. I don't expect performance impact of taking the
lock unconditionally, because there won't be cache line sharing since it
is per-vq lock and the locking cost will be offset by removing the
feature check.

Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>

Thanks,
Maxime