linux-kernel - Re: [PATCH v19 104/130] KVM: TDX: Add a place holder for handler of TDX hypercalls (TDG.VP.VMCALL)

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Message-ID: <ZgqFhx7JjhzKXjqb@chao-email>
Date: Mon, 1 Apr 2024 17:59:35 +0800
From: Chao Gao <chao.gao@...el.com>
To: <isaku.yamahata@...el.com>
CC: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<isaku.yamahata@...il.com>, Paolo Bonzini <pbonzini@...hat.com>,
	<erdemaktas@...gle.com>, Sean Christopherson <seanjc@...gle.com>, Sagi Shahar
	<sagis@...gle.com>, Kai Huang <kai.huang@...el.com>, <chen.bo@...el.com>,
	<hang.yuan@...el.com>, <tina.zhang@...el.com>, Xiaoyao Li
	<xiaoyao.li@...el.com>, Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v19 104/130] KVM: TDX: Add a place holder for handler of
 TDX hypercalls (TDG.VP.VMCALL)

> static inline bool is_td_vcpu_created(struct vcpu_tdx *tdx)
> {
> 	return tdx->td_vcpu_created;
>@@ -897,6 +932,11 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
> 
> 	tdx_complete_interrupts(vcpu);
> 
>+	if (tdx->exit_reason.basic == EXIT_REASON_TDCALL)
>+		tdx->tdvmcall.rcx = vcpu->arch.regs[VCPU_REGS_RCX];

kvm_rcx_read()?

		
>+	else
>+		tdx->tdvmcall.rcx = 0;

RCX on TDVMCALL exit is supposed to be consumed by TDX module. I don't get why
caching it is necessary. Can tdx->tdvmcall be simply dropped?