KVM dynamically toggles the CPU_BASED_USE_MSR_BITMAPS execution control for nested guests based on whether or not both L0 and L1 want to pass through the same MSRs to L2. Preserve the last used value from vmcs02 so as to avoid multiple VMWRITEs to (re)set/(re)clear the bit on nested VM-Entry. Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> --- arch/x86/kvm/vmx/nested.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index cd1daf3b63a4..e4d363661ae7 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2029,6 +2029,8 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) */ exec_control &= ~CPU_BASED_USE_IO_BITMAPS; exec_control |= CPU_BASED_UNCOND_IO_EXITING; + if (!(exec_controls_get(vmx) & CPU_BASED_USE_MSR_BITMAPS)) + exec_control &= ~CPU_BASED_USE_MSR_BITMAPS; exec_controls_set(vmx, exec_control); /* -- 2.21.0
