On Mon, Aug 05, 2013 at 07:27:33PM +0800, Arthur Chunqi Li wrote: > On Mon, Aug 5, 2013 at 4:07 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: > > From: Nadav Har'El <nyh@xxxxxxxxxx> > > > > Recent KVM, since http://kerneltrap.org/mailarchive/linux-kvm/2010/5/2/6261577 > > switch the EFER MSR when EPT is used and the host and guest have different > > NX bits. So if we add support for nested EPT (L1 guest using EPT to run L2) > > and want to be able to run recent KVM as L1, we need to allow L1 to use this > > EFER switching feature. > > > > To do this EFER switching, KVM uses VM_ENTRY/EXIT_LOAD_IA32_EFER if available, > > and if it isn't, it uses the generic VM_ENTRY/EXIT_MSR_LOAD. This patch adds > > support for the former (the latter is still unsupported). > > > > Nested entry and exit emulation (prepare_vmcs_02 and load_vmcs12_host_state, > > respectively) already handled VM_ENTRY/EXIT_LOAD_IA32_EFER correctly. So all > > that's left to do in this patch is to properly advertise this feature to L1. > > > > Note that vmcs12's VM_ENTRY/EXIT_LOAD_IA32_EFER are emulated by L0, by using > > vmx_set_efer (which itself sets one of several vmcs02 fields), so we always > > support this feature, regardless of whether the host supports it. > > > > Reviewed-by: Orit Wasserman <owasserm@xxxxxxxxxx> > > Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx> > > Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx> > > Signed-off-by: Xinhao Xu <xinhao.xu@xxxxxxxxx> > > Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx> > > Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx> > > --- > > arch/x86/kvm/vmx.c | 23 ++++++++++++++++------- > > 1 file changed, 16 insertions(+), 7 deletions(-) > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > index e999dc7..27efa6a 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -2198,7 +2198,8 @@ static __init void nested_vmx_setup_ctls_msrs(void) > > #else > > nested_vmx_exit_ctls_high = 0; > > #endif > > - nested_vmx_exit_ctls_high |= VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR; > > + nested_vmx_exit_ctls_high |= (VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR | > > + VM_EXIT_LOAD_IA32_EFER); > Gleb, why we don't need to check whether host supports > VM_EXIT_LOAD_IA32_EFER here, as what you noted in my > VM_EXIT_LOAD_IA32_PAT patch? Nested VMX completely emulates the capability. It calls vmx_set_efer() which suppose to handle hosts without VM_EXIT_LOAD_IA32_EFER support. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
