On 07/12/17 17:06, Christoffer Dall wrote: > Some system registers do not affect the host kernel's execution and can > therefore be loaded when we are about to run a VCPU and we don't have to > restore the host state to the hardware before the time when we are > actually about to return to userspace or schedule out the VCPU thread. > > The EL1 system registers and the userspace state registers, which only > affect EL0 execution, do not affect the host kernel's execution. > > The 32-bit system registers are not used by a VHE host kernel and > therefore don't need to be saved/restored on every entry/exit to/from > the guest, but can be deferred to vcpu_load and vcpu_put, respectively. Note that they are not used by the !VHE host kernel either, and I believe they could be deferred too, although that would imply a round trip to HYP to save/restore them. We already have such a hook there when configuring ICH_VMCR_EL2, so we may not need much of a new infrastructure. What do you think? M. -- Jazz is not dead. It just smells funny...
