On Fri, Sep 25, 2020 at 11:06:10PM +0200, Paolo Bonzini wrote: > On 25/09/20 19:12, Sean Christopherson wrote: > >> Do we actually want to prevent *all* ioctls? E.g. when 'vm bugged' > >> condition is triggered userspace may want to extract some information to > >> assist debugging but even things like KVM_GET_[S]REGS will just return > >> -EIO. I'm not sure it is generally safe to enable *everything* (except > >> for KVM_RUN which should definitely be forbidden) so maybe your approach > >> is preferable. > > > > The answer to this probably depends on the answer to the first question of > > when it's appropriate to use KVM_BUG(). E.g. if we limit usage to fatal or > > dangrous cases, then blocking all ioctls() is probably the right thing do do. > > I think usage should be limited to dangerous cases, basically WARN_ON > level. However I agree with Vitaly that KVM_GET_* should be allowed. Makes sense. On the topic of feedback from Vitaly, while dredging through my mailbox I rediscovered his suggestion of kvm->kvm_internal_bug (or maybe just kvm->internal_bug) instead of kvm->vm_bugged[*]. Like past me, I like the "internal" variants better. [*] https://lkml.kernel.org/r/20190930153358.GD14693@xxxxxxxxxxxxxxx > The other question is whether to return -EIO or KVM_EXIT_INTERNAL_ERROR. > The latter is more likely to be handled already by userspace. And probably less confusing for unsuspecting users. E.g. -EIO is most likely to be interpreted as "I screwed up", whereas KVM_EXIT_INTERNAL_ERROR will correctly be read as "KVM screwed up".
