On Tue, Jan 30, 2018 at 3:50 PM, KarimAllah Ahmed <karahmed@xxxxxxxxxx> wrote: > Okay, I took a second look at the code (specially > nested_vmx_merge_msr_bitmap). > > This means that I simply should not touch the MSR bitmap in set_msr in > case of nested, I just need to properly update the l02 msr_bitmap in > nested_vmx_merge_msr_bitmap. As in here: > > http://git.infradead.org/linux-retpoline.git/commitdiff/d90eedebdd16bb00741a2c93bc13c5e444c99c2b > > or am I still missing something? (sorry, did not actually look at the > nested code before!) + if (cpu_has_vmx_msr_bitmap() && data && + !vmx->save_spec_ctrl_on_exit) { + vmx->save_spec_ctrl_on_exit = true; + + if (is_guest_mode(vcpu)) + break; As Paolo suggested, the test for !is_guest_mode (vcpu) should just be folded into the condition above. If you aren't clearing a 'W' bit in the MSR permission bitmap, there's no need to set vmx->save_spec_ctrl_on_exit. + + vmx_disable_intercept_for_msr(vmx->vmcs01.msr_bitmap, + MSR_IA32_SPEC_CTRL, + MSR_TYPE_RW); + } + break; ... + if (guest_cpuid_has(vcpu, X86_FEATURE_IBRS)) { + nested_vmx_disable_intercept_for_msr( + msr_bitmap_l1, msr_bitmap_l0, + MSR_IA32_SPEC_CTRL, + MSR_TYPE_R | MSR_TYPE_W); + } + However, here, you should set vmx->save_spec_ctrl_on_exit if nested_vmx_disable_intercept_for_msr clears the 'W' bit for MSR_IA32_SPEC_CTRL in msr_bitmap_l0. Perhaps this would be easier if nested_vmx_disable_intercept_for_msr returned something indicative of which bits it cleared (if any).
