On 14/12/16 12:05, Russell King - ARM Linux wrote: > On Wed, Dec 14, 2016 at 11:56:49AM +0000, Mark Rutland wrote: >> On Wed, Dec 14, 2016 at 10:46:35AM +0000, Russell King wrote: >>> When we soft-reboot (eg, kexec) from one kernel into the next, we need >>> to ensure that we enter the new kernel in the same processor mode as >>> when we were entered, so that (eg) the new kernel can install its own >>> hypervisor - the old kernel's hypervisor will have been overwritten. >>> >>> In order to do this, we need to pass a flag to cpu_reset() so it knows >>> what to do, and we need to modify the kernel's own hypervisor stub to >>> allow it to handle a soft-reboot. >>> >>> As we are always guaranteed to install our own hypervisor if we're >>> entered in HYP32 mode, and KVM will have moved itself out of the way >>> on kexec/normal reboot, we can assume that our hypervisor is in place >>> when we want to kexec, so changing our hypervisor API should not be a >>> problem. >> >> Just to check, does that also hold true for kdump? >> >> I haven't gone digging yet, but it looks like KVM might still be >> installed, rather than the hyp stub, and we might need some logic to >> ensure that it's torn down... > > The same problem will be true of ARM64 - I don't see any solution to > that in the present state. > >>> @@ -51,7 +52,9 @@ static void __soft_restart(void *addr) >>> >>> /* Switch to the identity mapping. */ >>> phys_reset = (phys_reset_t)virt_to_idmap(cpu_reset); >>> - phys_reset((unsigned long)addr); >>> + >>> + /* original stub should be restored by kvm */ >>> + phys_reset((unsigned long)addr, is_hyp_mode_available()); >> >> ... otherwise here we'd call into the KVM hyp code in a potentially >> confusing manner. >> >> Otherwise, this looks fine to me. > > The only thing that I can think which would resolve that would be to > lay down a standard API for the hyp code, so things like reboot into > hyp mode can work irrespective of the hyp stub in place. That looks like a sensible thing to do. I'll look into it. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
