On Tue, Jul 02, 2013 at 04:28:56PM +0200, Jan Kiszka wrote: > On 2013-07-02 15:59, Gleb Natapov wrote: > > On Tue, Jul 02, 2013 at 03:01:24AM +0000, Zhang, Yang Z wrote: > >> Since this series is pending in mail list for long time. And it's really a big feature for Nested. Also, I doubt the original authors(Jun and Nahav)should not have enough time to continue it. So I will pick it up. :) > >> > >> See comments below: > >> > >> Paolo Bonzini wrote on 2013-05-20: > >>> Il 19/05/2013 06:52, Jun Nakajima ha scritto: > >>>> 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. > >>>> > >>>> Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx> > >>>> Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx> > >>>> Signed-off-by: Xinhao Xu <xinhao.xu@xxxxxxxxx> > >>>> --- > >>>> 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 260a919..fb9cae5 100644 > >>>> --- a/arch/x86/kvm/vmx.c > >>>> +++ b/arch/x86/kvm/vmx.c > >>>> @@ -2192,7 +2192,8 @@ 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); > >>>> > >>>> /* entry controls */ > >>>> rdmsr(MSR_IA32_VMX_ENTRY_CTLS, > >>>> @@ -2201,8 +2202,8 @@ static __init void nested_vmx_setup_ctls_msrs(void) > >>>> nested_vmx_entry_ctls_low = > >>> VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR; > >>>> nested_vmx_entry_ctls_high &= > >>>> VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_IA32E_MODE; > >>>> - nested_vmx_entry_ctls_high |= > >>> VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR; > >>>> - > >>>> + nested_vmx_entry_ctls_high |= > >>> (VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR | > >>>> + VM_ENTRY_LOAD_IA32_EFER); > >>>> /* cpu-based controls */ > >>>> rdmsr(MSR_IA32_VMX_PROCBASED_CTLS, > >>>> nested_vmx_procbased_ctls_low, nested_vmx_procbased_ctls_high); > >>>> @@ -7492,10 +7493,18 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, > >>> struct vmcs12 *vmcs12) > >>>> vcpu->arch.cr0_guest_owned_bits &= ~vmcs12->cr0_guest_host_mask; > >>>> vmcs_writel(CR0_GUEST_HOST_MASK, > >>> ~vcpu->arch.cr0_guest_owned_bits); > >>>> > >>>> - /* Note: IA32_MODE, LOAD_IA32_EFER are modified by vmx_set_efer > >>> below */ > >>>> - vmcs_write32(VM_EXIT_CONTROLS, > >>>> - vmcs12->vm_exit_controls | vmcs_config.vmexit_ctrl); > >>>> - vmcs_write32(VM_ENTRY_CONTROLS, vmcs12->vm_entry_controls | > >>>> + /* L2->L1 exit controls are emulated - the hardware exit is to L0 so > >>>> + * we should use its exit controls. Note that IA32_MODE, LOAD_IA32_EFER > >>>> + * bits are further modified by vmx_set_efer() below. > >>>> + */ > >>>> + vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl); > >> This is wrong. We cannot use L0 exit control directly. > >> LOAD_PERF_GLOBAL_CTRL, LOAD_HOST_EFE, LOAD_HOST_PAT, ACK_INTR_ON_EXIT should use host's exit control. But others, still need use (vmcs12|host). > >> > > I do not see why. We always intercept DR7/PAT/EFER, so save is emulated > > too. Host address space size always come from L0 and preemption timer is > > not supported for nested IIRC and when it will be host will have to save > > it on exit anyway for correct emulation. > > Preemption timer is already supported and works fine as far as I tested. > KVM doesn't use it for L1, so we do not need to save/restore it - IIRC. > So what happens if L1 configures it to value X after X/2 ticks L0 exit happen and L0 gets back to L2 directly. The counter will be X again instead of X/2. -- 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
