On 30/01/2018 17:49, Jim Mattson wrote: > On Tue, Jan 30, 2018 at 1:00 PM, KarimAllah Ahmed <karahmed@xxxxxxxxxx> wrote: >> Ooops! I did not think at all about nested :) >> >> This should be addressed now, I hope: >> >> http://git.infradead.org/linux-retpoline.git/commitdiff/f7f0cbba3e0cffcee050a8a5a9597a162d57e572 > > + if (cpu_has_vmx_msr_bitmap() && data && > + !vmx->save_spec_ctrl_on_exit) { > + vmx->save_spec_ctrl_on_exit = true; > + > + msr_bitmap = is_guest_mode(vcpu) ? > vmx->nested.vmcs02.msr_bitmap : > + > vmx->vmcs01.msr_bitmap; > + vmx_disable_intercept_for_msr(msr_bitmap, > + MSR_IA32_SPEC_CTRL, > + MSR_TYPE_RW); > + } > > There are two ways to get to this point in vmx_set_msr while > is_guest_mode(vcpu) is true: > 1) L0 is processing vmcs12's VM-entry MSR load list on emulated > VM-entry (see enter_vmx_non_root_mode). > 2) L2 tried to execute WRMSR, writes to the MSR are intercepted in > vmcs02's MSR permission bitmap, and writes to the MSR are not > intercepted in vmcs12's MSR permission bitmap. > > In the first case, disabling the intercepts for the MSR in > vmx->nested.vmcs02.msr_bitmap is incorrect, because we haven't yet > determined that the intercepts are clear in vmcs12's MSR permission > bitmap. > In the second case, disabling *both* of the intercepts for the MSR in > vmx->nested.vmcs02.msr_bitmap is incorrect, because we don't know that > the read intercept is clear in vmcs12's MSR permission bitmap. > Furthermore, disabling the write intercept for the MSR in > vmx->nested.vmcs02.msr_bitmap is somewhat fruitless, because > nested_vmx_merge_msr_bitmap is just going to undo that change on the > next emulated VM-entry. > Let's keep the original code from David, touching the L0->L1 MSR bitmap unconditionally, and possibly add an "&& !is_guest_mode (vcpu)" to the condition. Paolo
