linux-kernel - Re: [RFC PATCH v5 091/104] KVM: TDX: Handle TDX PV CPUID hypercall

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Message-ID: <adea5393-cbe9-3344-0ef5-461a72321f72@redhat.com>
Date:   Thu, 7 Apr 2022 15:16:36 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 091/104] KVM: TDX: Handle TDX PV CPUID hypercall

On 3/4/22 20:49, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Wire up TDX PV CPUID hypercall to the KVM backend function.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/vmx/tdx.c | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 53f59fb92dcf..f7c9170d596a 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -893,6 +893,30 @@ static int tdx_emulate_vmcall(struct kvm_vcpu *vcpu)
>   	return 1;
>   }
>   
> +static int tdx_emulate_cpuid(struct kvm_vcpu *vcpu)
> +{
> +	u32 eax, ebx, ecx, edx;
> +
> +	/* EAX and ECX for cpuid is stored in R12 and R13. */
> +	eax = tdvmcall_p1_read(vcpu);
> +	ecx = tdvmcall_p2_read(vcpu);
> +
> +	kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true);
> +
> +	/*
> +	 * The returned value for CPUID (EAX, EBX, ECX, and EDX) is stored into
> +	 * R12, R13, R14, and R15.
> +	 */
> +	tdvmcall_p1_write(vcpu, eax);
> +	tdvmcall_p2_write(vcpu, ebx);
> +	tdvmcall_p3_write(vcpu, ecx);
> +	tdvmcall_p4_write(vcpu, edx);
> +
> +	tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
> +
> +	return 1;
> +}
> +
>   static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>   {
>   	struct vcpu_tdx *tdx = to_tdx(vcpu);
> @@ -904,6 +928,9 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>   		return tdx_emulate_vmcall(vcpu);
>   
>   	switch (tdvmcall_exit_reason(vcpu)) {
> +	case EXIT_REASON_CPUID:
> +		return tdx_emulate_cpuid(vcpu);
> +
>   	default:
>   		break;
>   	}

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>

but I don't think tdvmcall_*_{read,write} add much.

Paolo