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Date: Wed, 29 Jun 2022 03:13:56 -0700 From: Isaku Yamahata <isaku.yamahata@...il.com> To: Sagi Shahar <sagis@...gle.com> Cc: "Yamahata, Isaku" <isaku.yamahata@...el.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>, Erdem Aktas <erdemaktas@...gle.com>, Sean Christopherson <seanjc@...gle.com> Subject: Re: [RFC PATCH v6 090/104] KVM: TDX: Handle TDX PV CPUID hypercall On Tue, Jun 14, 2022 at 11:15:00AM -0700, Sagi Shahar <sagis@...gle.com> wrote: > On Thu, May 5, 2022 at 11:16 AM <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 | 22 ++++++++++++++++++++++ > > 1 file changed, 22 insertions(+) > > > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > > index 9c712f661a7c..c7cdfee397ec 100644 > > --- a/arch/x86/kvm/vmx/tdx.c > > +++ b/arch/x86/kvm/vmx/tdx.c > > @@ -946,12 +946,34 @@ 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_a0_read(vcpu); > > + ecx = tdvmcall_a1_read(vcpu); > > + > > + kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true); > > According to the GHCI spec section 3.6 > (TDG.VP.VMCALL<Instruction.CPUID>) we should return > VMCALL_INVALID_OPERAND if an invalid CPUID is requested. > > kvm_cpuid already returns false in this case so we should use that > return value to set the tdvmcall return code in case of invalid leaf. Based on CPUID instruction, cpuid results in #UD when lock prefix is used or earlier CPU that doesn't support cpuid instruction. So I'm not sure what CPUID input result in INVALID_OPERAND error. Does the following make sense for you? --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1347,7 +1347,7 @@ static int tdx_emulate_cpuid(struct kvm_vcpu *vcpu) eax = tdvmcall_a0_read(vcpu); ecx = tdvmcall_a1_read(vcpu); - kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true); + kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, false); tdvmcall_a0_write(vcpu, eax); tdvmcall_a1_write(vcpu, ebx); thanks, -- Isaku Yamahata <isaku.yamahata@...il.com>
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