Re: [PATCH v5 01/14] nEPT: Support LOAD_IA32_EFER entry/exit controls for L1

Orit Wasserman
2013-08-01T11:21:25Z

On 07/31/2013 05:48 PM, Gleb Natapov wrote:
> From: Nadav Har'El <nyh@il.ibm.com>
>
> 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@il.ibm.com>
> Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
> Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> ---
> 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);
>
> /* entry controls */
> rdmsr(MSR_IA32_VMX_ENTRY_CTLS,
> @@ -2207,8 +2208,8 @@ 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);
> @@ -7529,10 +7530,18 @@ 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 VM_EXIT_LOAD_IA32_EFER
> + * bits are further modified by vmx_set_efer() below.
> + */
> + vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl);
> +
> + /* vmcs12's VM_ENTRY_LOAD_IA32_EFER and VM_ENTRY_IA32E_MODE are
> + * emulated by vmx_set_efer(), below.
> + */
> + vmcs_write32(VM_ENTRY_CONTROLS,
> + (vmcs12->vm_entry_controls & ~VM_ENTRY_LOAD_IA32_EFER &
> + ~VM_ENTRY_IA32E_MODE) |
> (vmcs_config.vmentry_ctrl & ~VM_ENTRY_IA32E_MODE));
>
> if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PAT)
>

Reviewed-by: Orit Wasserman <owasserm@redhat.com>