On Thu, May 5, 2022 at 11:16 AM <isaku.yamahata@xxxxxxxxx> wrote:
>
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Wire up TDX PV rdmsr/wrmsr hypercall to the KVM backend function.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/vmx/tdx.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index f46825843a8b..1518a8c310d6 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1169,6 +1169,39 @@ static int tdx_emulate_mmio(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> +static int tdx_emulate_rdmsr(struct kvm_vcpu *vcpu)
> +{
> + u32 index = tdvmcall_a0_read(vcpu);
> + u64 data;
> +
> + if (kvm_get_msr(vcpu, index, &data)) {
kvm_get_msr and kvm_set_msr used to check the MSR permissions using
kvm_msr_allowed but that behaviour changed in "KVM: x86: Only do MSR
filtering when access MSR by rdmsr/wrmsr".
Now kvm_get_msr and kvm_set_msr skip these checks and will allow
access regardless of the permissions in the msr_filter.
These should be changed to kvm_get_msr_with_filter and
kvm_set_msr_with_filter or something similar that checks permissions
for MSR access.
> + trace_kvm_msr_read_ex(index);
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_INVALID_OPERAND);
> + return 1;
> + }
> + trace_kvm_msr_read(index, data);
> +
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
> + tdvmcall_set_return_val(vcpu, data);
> + return 1;
> +}
> +
> +static int tdx_emulate_wrmsr(struct kvm_vcpu *vcpu)
> +{
> + u32 index = tdvmcall_a0_read(vcpu);
> + u64 data = tdvmcall_a1_read(vcpu);
> +
> + if (kvm_set_msr(vcpu, index, data)) {
> + trace_kvm_msr_write_ex(index, data);
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_INVALID_OPERAND);
> + return 1;
> + }
> +
> + trace_kvm_msr_write(index, data);
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
> + return 1;
> +}
> +
> static int handle_tdvmcall(struct kvm_vcpu *vcpu)
> {
> if (tdvmcall_exit_type(vcpu))
> @@ -1183,6 +1216,10 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
> return tdx_emulate_io(vcpu);
> case EXIT_REASON_EPT_VIOLATION:
> return tdx_emulate_mmio(vcpu);
> + case EXIT_REASON_MSR_READ:
> + return tdx_emulate_rdmsr(vcpu);
> + case EXIT_REASON_MSR_WRITE:
> + return tdx_emulate_wrmsr(vcpu);
> default:
> break;
> }
> --
> 2.25.1
>
Sagi
