Re: [RFC PATCH v5 088/104] KVM: TDX: Add TDG.VP.VMCALL accessors to access guest vcpu registers

From: Kai Huang
Date: Thu Apr 07 2022 - 00:06:58 EST


On Fri, 2022-03-04 at 11:49 -0800, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> TDX defines ABI for the TDX guest to call hypercall with TDG.VP.VMCALL API.
> To get hypercall arguments and to set return values, add accessors to guest
> vcpu registers.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx/tdx.c | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index dc83414cb72a..8695836ce796 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -88,6 +88,41 @@ static __always_inline unsigned long tdexit_intr_info(struct kvm_vcpu *vcpu)
> return kvm_r9_read(vcpu);
> }
>
> +#define BUILD_TDVMCALL_ACCESSORS(param, gpr) \
> +static __always_inline \
> +unsigned long tdvmcall_##param##_read(struct kvm_vcpu *vcpu) \
> +{ \
> + return kvm_##gpr##_read(vcpu); \
> +} \
> +static __always_inline void tdvmcall_##param##_write(struct kvm_vcpu *vcpu, \
> + unsigned long val) \
> +{ \
> + kvm_##gpr##_write(vcpu, val); \
> +}
> +BUILD_TDVMCALL_ACCESSORS(p1, r12);
> +BUILD_TDVMCALL_ACCESSORS(p2, r13);
> +BUILD_TDVMCALL_ACCESSORS(p3, r14);
> +BUILD_TDVMCALL_ACCESSORS(p4, r15);

Are they needed? Do those helpers provide more information than just using
kvm_{reg}_read/write()?

> +
> +static __always_inline unsigned long tdvmcall_exit_type(struct kvm_vcpu *vcpu)
> +{
> + return kvm_r10_read(vcpu);
> +}
> +static __always_inline unsigned long tdvmcall_exit_reason(struct kvm_vcpu *vcpu)
> +{
> + return kvm_r11_read(vcpu);
> +}
> +static __always_inline void tdvmcall_set_return_code(struct kvm_vcpu *vcpu,
> + long val)
> +{
> + kvm_r10_write(vcpu, val);
> +}
> +static __always_inline void tdvmcall_set_return_val(struct kvm_vcpu *vcpu,
> + unsigned long val)
> +{
> + kvm_r11_write(vcpu, val);
> +}
> +
> static inline bool is_td_vcpu_created(struct vcpu_tdx *tdx)
> {
> return tdx->tdvpr.added;