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

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Message-ID: <837bbbc7-e7f3-4362-a745-310fe369f43d@intel.com>
Date: Fri, 22 Nov 2024 16:33:27 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: 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
Cc: 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, yan.y.zhao@...el.com,
 chao.gao@...el.com, weijiang.yang@...el.com
Subject: Re: [PATCH 2/7] KVM: TDX: Implement TDX vcpu enter/exit path

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 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;
>>> +}
>>> +
> [...]