On Tue, Mar 24, 2020 at 11:40:18AM +0100, Thomas Gleixner wrote: > Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes: > > On 3/24/2020 1:10 AM, Thomas Gleixner wrote: > >> Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes: > >> > >>> Change sld_off to sld_disable, which means disabling feature split lock > >>> detection and it cannot be used in kernel nor can kvm expose it guest. > >>> Of course, the X86_FEATURE_SPLIT_LOCK_DETECT is not set. > >>> > >>> Add a new optioin sld_kvm_only, which means kernel turns split lock > >>> detection off, but kvm can expose it to guest. > >> > >> What's the point of this? If the host is not clean, then you better fix > >> the host first before trying to expose it to guests. > > > > It's not about whether or not host is clean. It's for the cases that > > users just don't want it enabled on host, to not break the applications > > or drivers that do have split lock issue. > > It's very much about whether the host is split lock clean. > > If your host kernel is not, then this wants to be fixed first. If your > host application is broken, then either fix it or use "warn". The "kvm only" option was my suggestion. The thought was to provide a way for users to leverage KVM to debug/test kernels without having to have a known good kernel and/or to minimize the risk of crashing their physical system. E.g. debug a misbehaving driver by assigning its associated device to a guest.
