linux-kernel - [PATCH v10 102/108] KVM: TDX: Handle TDG.VP.VMCALL<GetTdVmCallInfo> hypercall

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Message-Id: <ac362386d3a589f10e8f8353c89ad3e14522e12d.1667110240.git.isaku.yamahata@intel.com>
Date:   Sat, 29 Oct 2022 23:23:43 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH v10 102/108] KVM: TDX: Handle TDG.VP.VMCALL<GetTdVmCallInfo> hypercall

From: Isaku Yamahata <isaku.yamahata@...el.com>

Implement TDG.VP.VMCALL<GetTdVmCallInfo> hypercall.  If the input value is
zero, return success code and zero in output registers.

TDG.VP.VMCALL<GetTdVmCallInfo> hypercall is a subleaf of TDG.VP.VMCALL to
enumerate which TDG.VP.VMCALL sub leaves are supported.  This hypercall is
for future enhancement of the Guest-Host-Communication Interface (GHCI)
specification.  The GHCI version of 344426-001US defines it to require
input R12 to be zero and to return zero in output registers, R11, R12, R13,
and R14 so that guest TD enumerates no enhancement.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/vmx/tdx.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 4db552b60271..8e8ac1081ce4 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1068,6 +1068,20 @@ static int tdx_emulate_wrmsr(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int tdx_get_td_vm_call_info(struct kvm_vcpu *vcpu)
+{
+	if (tdvmcall_a0_read(vcpu))
+		tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_INVALID_OPERAND);
+	else {
+		tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
+		kvm_r11_write(vcpu, 0);
+		tdvmcall_a0_write(vcpu, 0);
+		tdvmcall_a1_write(vcpu, 0);
+		tdvmcall_a2_write(vcpu, 0);
+	}
+	return 1;
+}
+
 static int tdx_report_fatal_error(struct kvm_vcpu *vcpu)
 {
 	/*
@@ -1135,6 +1149,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
 		return tdx_emulate_rdmsr(vcpu);
 	case EXIT_REASON_MSR_WRITE:
 		return tdx_emulate_wrmsr(vcpu);
+	case TDG_VP_VMCALL_GET_TD_VM_CALL_INFO:
+		return tdx_get_td_vm_call_info(vcpu);
 	case TDG_VP_VMCALL_REPORT_FATAL_ERROR:
 		return tdx_report_fatal_error(vcpu);
 	case TDG_VP_VMCALL_MAP_GPA:
-- 
2.25.1