On 04/05/18 17:05, Dave Martin wrote: > From: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > > KVM/ARM differs from other architectures in having to maintain an > additional virtual address space from that of the host and the > guest, because we split the execution of KVM across both EL1 and > EL2. > > This results in a need to explicitly map data structures into EL2 > (hyp) which are accessed from the hyp code. As we are about to be > more clever with our FPSIMD handling on arm64, which stores data in > the task struct and uses thread_info flags, we will have to map > parts of the currently executing task struct into the EL2 virtual > address space. > > However, we don't want to do this on every KVM_RUN, because it is a > fairly expensive operation to walk the page tables, and the common > execution mode is to map a single thread to a VCPU. By introducing > a hook that architectures can select with > HAVE_KVM_VCPU_RUN_PID_CHANGE, we do not introduce overhead for > other architectures, but have a simple way to only map the data we > need when required for arm64. > > This patch introduces the framework only, and wires it up in the > arm/arm64 KVM common code. > > No functional change. > > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx> M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
