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

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Message-ID: <5bc95c6394a98ddfcdd5c8d333dc06e45c0e40af.camel@intel.com>
Date:   Thu, 07 Apr 2022 16:06:37 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 088/104] KVM: TDX: Add TDG.VP.VMCALL accessors to
 access guest vcpu registers

On Fri, 2022-03-04 at 11:49 -0800, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> 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@...el.com>
> ---
>  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;