linux-kernel - Re: [PATCH 2/7] KVM: TDX: Implement TDX vcpu enter/exit path

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Message-ID: <Z0gGBnTcFzY99/iG@yzhao56-desk.sh.intel.com>
Date: Thu, 28 Nov 2024 13:56:22 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Adrian Hunter <adrian.hunter@...el.com>
CC: Binbin Wu <binbin.wu@...ux.intel.com>, Xiaoyao Li <xiaoyao.li@...el.com>,
	<pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<dave.hansen@...ux.intel.com>, <rick.p.edgecombe@...el.com>,
	<kai.huang@...el.com>, <reinette.chatre@...el.com>,
	<tony.lindgren@...ux.intel.com>, <dmatlack@...gle.com>,
	<isaku.yamahata@...el.com>, <nik.borisov@...e.com>,
	<linux-kernel@...r.kernel.org>, <x86@...nel.org>, <chao.gao@...el.com>,
	<weijiang.yang@...el.com>
Subject: Re: [PATCH 2/7] KVM: TDX: Implement TDX vcpu enter/exit path

On Fri, Nov 22, 2024 at 04:33:27PM +0200, Adrian Hunter wrote:
> On 22/11/24 07:56, Binbin Wu wrote:
> > 
> > 
> > 
> > On 11/22/2024 1:23 PM, Xiaoyao Li wrote:
> > [...]
> >>> +
> >>> +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
> >>> +{
> >>> +    struct vcpu_tdx *tdx = to_tdx(vcpu);
> >>> +
> >>> +    /* TDX exit handle takes care of this error case. */
> >>> +    if (unlikely(tdx->state != VCPU_TD_STATE_INITIALIZED)) {
> >>> +        /* Set to avoid collision with EXIT_REASON_EXCEPTION_NMI. */
> >>
> >> It seems the check fits better in tdx_vcpu_pre_run().
> > 
> > Indeed, it's cleaner to move the check to vcpu_pre_run.
> > Then no need to set the value to vp_enter_ret, and the comments are not
> > needed.
> 
> And we can take out the same check in tdx_handle_exit()
> because it won't get there if ->vcpu_pre_run() fails.

And also check for TD_STATE_RUNNABLE in tdx_vcpu_pre_run()?

> > 
> >>
> >> And without the patch of how TDX handles Exit (i.e., how deal with vp_enter_ret), it's hard to review this comment.
> >>
> >>> +        tdx->vp_enter_ret = TDX_SW_ERROR;
> >>> +        return EXIT_FASTPATH_NONE;
> >>> +    }
> >>> +
> >>> +    trace_kvm_entry(vcpu, force_immediate_exit);
> >>> +
> >>> +    tdx_vcpu_enter_exit(vcpu);
> >>> +
> >>> +    vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
> >>> +    trace_kvm_exit(vcpu, KVM_ISA_VMX);
> >>> +
> >>> +    return EXIT_FASTPATH_NONE;
> >>> +}
> >>> +
> > [...]
>