On Mon, Feb 25, 2019 at 09:27:13PM +0800, Yang Weijiang wrote:
> The CET runtime settings, i.e., CET state control bits(IA32_U_CET/
> IA32_S_CET), CET SSP(IA32_PL3_SSP/IA32_PL0_SSP) and SSP table address
> (IA32_INTERRUPT_SSP_TABLE_ADDR) are task/thread specific, therefore,
> OS needs to save/restore the states properly during context switch,
> e.g., task/thread switching, interrupt/exception handling, it uses
> xsaves/xrstors to achieve that.
>
> The difference between VMCS CET area fields and xsave CET area, is that
> the former is for state retention during Guest/Host context
> switch while the latter is for state retention during OS execution.
>
> Linux currently doesn't support CPL1 and CPL2, so SSPs for these level
> are skipped here.
But don't we want to allow a guest to access the MSRs regardless of
the host kernel's behavior?
> Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 7bbb8b26e901..89ee086e1729 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -11769,6 +11769,7 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
> static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
> {
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> + unsigned long *msr_bitmap;
>
> if (cpu_has_secondary_exec_ctrls()) {
> vmx_compute_secondary_exec_control(vmx);
> @@ -11786,6 +11787,18 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
> nested_vmx_cr_fixed1_bits_update(vcpu);
> nested_vmx_entry_exit_ctls_update(vcpu);
> }
> +
> + msr_bitmap = vmx->vmcs01.msr_bitmap;
> +
> + if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) |
This should be a logical OR, not a bitwise OR.
> + guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);
> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
> + }
> +
> }
>
> static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> --
> 2.17.1
>
