> From: Nicolin Chen <nicolinc@xxxxxxxxxx> > Sent: Thursday, June 16, 2022 8:03 AM > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > The KVM mechanism for controlling wbinvd is based on OR of the coherency > property of all devices attached to a guest, no matter those devices are > attached to a single domain or multiple domains. > > So, there is no value in trying to push a device that could do enforced > cache coherency to a dedicated domain vs re-using an existing domain > which is non-coherent since KVM won't be able to take advantage of it. > This just wastes domain memory. > > Simplify this code and eliminate the test. This removes the only logic > that needed to have a dummy domain attached prior to searching for a > matching domain and simplifies the next patches. > > It's unclear whether we want to further optimize the Intel driver to > update the domain coherency after a device is detached from it, at > least not before KVM can be verified to handle such dynamics in related > emulation paths (wbinvd, vcpu load, write_cr0, ept, etc.). In reality > we don't see an usage requiring such optimization as the only device > which imposes such non-coherency is Intel GPU which even doesn't > support hotplug/hot remove. > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
