On Wed, Jan 23, 2019 at 04:59:08AM +0800, Yang Weijiang wrote:
> "Load Guest CET state" bit controls whether guest CET states
> will be loaded on Guest entry. Before doing that, KVM needs
> to check if CET feature is exposed to Guest.
>
> Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 68c0e5e41cb1..9c8cecac80ea 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -55,6 +55,7 @@
> #include <asm/mmu_context.h>
> #include <asm/spec-ctrl.h>
> #include <asm/mshyperv.h>
> +#include <asm/cet.h>
>
> #include "trace.h"
> #include "pmu.h"
> @@ -4065,6 +4066,18 @@ static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu,
> return !(val & ~valid_bits);
> }
>
> +static int vmx_guest_cet_cap(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_cpuid_entry2 *best;
> + int r = 0;
> +
> + best = kvm_find_cpuid_entry(vcpu, 7, 0);
> + if (best && best->function == 0x7)
> + r = (best->ecx & bit(X86_FEATURE_SHSTK)) |
> + (best->edx & bit(X86_FEATURE_IBT)) ? 1 : 0;
> + return r;
> +}
> +
> static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
> {
> switch (msr->index) {
> @@ -5409,6 +5422,26 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> return 1;
> }
>
> + /*
> + * To enable Guest CET, first check if Guest CET feature is
> + * available, if it's not available but its CR4.CET is being set,
> + * return a fault to Guest; then check if Host CET is enabled and
> + * CR4.CET is toggled, if they are, then enable loading CET state
Comment doesn't match the code. Comment says "toggled", code is just
looking at "enabled".
> + * bit in entry control, otherwise, clear the bit to
> + * disable guest CET state loading.
What happens to CET state if the control is clear? Is host state
retained but inaccessible?
> + */
> + if (vmx_guest_cet_cap(vcpu)) {
Why not?
if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
> + if (hw_cr4 & 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;
> + }
> +
> if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
> return 1;
>
> --
> 2.17.1
>
