linux-kernel - Re: [RFC PATCH v5 092/104] KVM: TDX: Handle TDX PV HLT hypercall

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Date:   Thu, 7 Apr 2022 15:56:01 +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 092/104] KVM: TDX: Handle TDX PV HLT hypercall

On 3/4/22 20:49, isaku.yamahata@...el.com wrote:
> +	bool interrupt_disabled = tdvmcall_p1_read(vcpu);

Where is R12 documented for TDG.VP.VMCALL<Instruction.HLT>?

> +		 * Virtual interrupt can arrive after TDG.VM.VMCALL<HLT> during
> +		 * the TDX module executing.  On the other hand, KVM doesn't
> +		 * know if vcpu was executing in the guest TD or the TDX module.

I don't understand this; why isn't it enough to check PI.ON or something 
like that as part of HLT emulation?

> +		details.full = td_state_non_arch_read64(
> +			to_tdx(vcpu), TD_VCPU_STATE_DETAILS_NON_ARCH);

TDX documentation says "the meaning of the field may change with Intel 
TDX module version", where is this field documented?  I cannot find any 
"other guest state" fields in the TDX documentation.

Paolo

> +		if (details.vmxip)
> +			return 1;
> +	}
> +
> +	return kvm_emulate_halt_noskip(vcpu);