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

From: Paolo Bonzini
Date: Thu Apr 07 2022 - 09:16:50 EST


On 3/4/22 20:49, isaku.yamahata@xxxxxxxxx wrote:
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Wire up TDX PV CPUID hypercall to the KVM backend function.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
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@xxxxxxxxxx>

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

Paolo