On Wed, May 22, 2019 at 03:00:58PM +0800, Yang Weijiang wrote:
> "Load Guest CET state" bit controls whether Guest CET states
> will be loaded at Guest entry. Before doing that, KVM needs
> to check if CPU CET feature is available to Guest.
>
> Note: SHSTK and IBT features share one control MSR:
> MSR_IA32_{U,S}_CET, which means it's difficult to hide
> one feature from another in the case of SHSTK != IBT,
> after discussed in community, it's agreed to allow Guest
> control two features independently as it won't introduce
> security hole.
>
> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> Co-developed-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/vmx/vmx.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 9321da538f65..1c0d487a4037 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -47,6 +47,7 @@
> #include <asm/spec-ctrl.h>
> #include <asm/virtext.h>
> #include <asm/vmx.h>
> +#include <asm/cet.h>
Is this include actually needed? I haven't attempted to compile, but a
glance everything should be in cpufeatures.h or vmx.h.
> #include "capabilities.h"
> #include "cpuid.h"
> @@ -2929,6 +2930,17 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> if (!nested_vmx_allowed(vcpu) || is_smm(vcpu))
> return 1;
> }
> + if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
> + guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
> + if (cr4 & X86_CR4_CET)
> + vmcs_set_bits(VM_ENTRY_CONTROLS,
> + VM_ENTRY_LOAD_GUEST_CET_STATE);
> + else
> + vmcs_clear_bits(VM_ENTRY_CONTROLS,
> + VM_ENTRY_LOAD_GUEST_CET_STATE);
> + } else if (cr4 & X86_CR4_CET) {
> + return 1;
> + }
Don't we also need to check for host CET support prior to toggling
VM_ENTRY_LOAD_GUEST_CET_STATE?
>
> if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
> return 1;
> --
> 2.17.2
>
