On 14.08.2013, at 11:23, Peter Maydell wrote: > On 14 August 2013 10:11, Alexander Graf <ag...@suse.de> wrote: >> You're right, the main difference is that KVM doesn't have any >> idea what a "host" style CPU is. It only knows how to report to QEMU >> what the current host CPU would be, so that anything from VCPU_INIT >> onwards is 100% identical regardless of whether the user said >> -cpu host or -cpu xxx. >> >> I'm still puzzled on how this will work with BIG.little btw. > > The rough idea is that for BIG.little the kernel must trap the > ID registers at least (so that the vcpu seems consistent to the > guest whether it's running on the big or the little core). For > "-cpu host" the guest would see whatever is the most low-overhead > for the kernel to provide (ie assuming the big and little CPUs > are roughly-similar you could make -cpu host provide something > that looks to the guest like the big CPU and don't have to trap > quite as much as you would for providing a vcpu that wasn't the > same as either the big or little one).
So -cpu host in this case wouldn't actually expose the host CPU 1:1, but instead a cortex-a15 even when it's run on an a7 BIG.little core. I see. Alex
