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. Jan
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