Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Wed, Aug 14, 2024, Vitaly Kuznetsov wrote: >> What I meant is something along these lines (untested): >> >> diff --git a/arch/x86/kvm/vmx/vmx_onhyperv.h b/arch/x86/kvm/vmx/vmx_onhyperv.h >> index eb48153bfd73..e2d8c67d0cad 100644 >> --- a/arch/x86/kvm/vmx/vmx_onhyperv.h >> +++ b/arch/x86/kvm/vmx/vmx_onhyperv.h >> @@ -104,6 +104,14 @@ static inline void evmcs_load(u64 phys_addr) >> struct hv_vp_assist_page *vp_ap = >> hv_get_vp_assist_page(smp_processor_id()); >> >> + /* >> + * When enabling eVMCS, KVM verifies that every CPU has a valid hv_vp_assist_page() >> + * and aborts enabling the feature otherwise. CPU onlining path is also checked in >> + * vmx_hardware_enable(). With this, it is impossible to reach here with vp_ap == NULL >> + * but compilers may still complain. >> + */ >> + BUG_ON(!vp_ap); > > A full BUG_ON() is overkill, and easily avoided. If we want to add a sanity > check here and do more than just WARN, then it's easy enough to plumb in @vcpu > and make this a KVM_BUG_ON() so that the VM dies, i.e. so that KVM doesn't risk > corrupting the guest somehow. > I'm still acting under the impression this is an absolutely impossible situation :-) AFAICS, we only call evmcs_load() from vmcs_load() but this one doesn't have @vcpu/@kvm either and I wasn't sure it's worth the effort to do the plumbing (or am I missing an easy way to go back from @vmcs to @vcpu?). On the other hand, vmcs_load() should not be called that ofter so if we prefer to have @vcpu there for some other reason -- why not. -- Vitaly
