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

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Message-ID: <27a59f1a-ea74-2d75-0739-5521e7638c68@redhat.com>
Date:   Fri, 8 Apr 2022 11:57:37 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>
Cc:     Sean Christopherson <seanjc@...gle.com>, isaku.yamahata@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>
Subject: Re: [RFC PATCH v5 092/104] KVM: TDX: Handle TDX PV HLT hypercall

On 4/8/22 06:58, Isaku Yamahata wrote:
> On Thu, Apr 07, 2022 at 05:56:05PM +0200,
> Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
>> You didn't answer the other question, which is "Where is R12 documented for
>> TDG.VP.VMCALL<Instruction.HLT>?" though...  Should I be worried? :)
> 
> It's publicly documented.
> 
> Guest-Host-Communication Interface(GHCI) spec, 344426-003US Feburary 2022.
> 3.8 TDG.VP.VMCALL<Instruction.HLT>
> R12 Interrupt Blocked Flag.
>      The TD is expected to clear this flag iff RFLAGS.IF == 1 or the TDCALL instruction
>      (that invoked TDG.VP.TDVMCALL(Instruction.HLT)) immediately follows an STI
>      instruction, otherwise this flag should be set.

Oh, Google doesn't know about this version of the spec...  It can be 
downloaded from 
https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html 
though.

I also found VCPU_STATE_DETAILS in 
https://www.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1.0-public-spec-v0.931.pdf:

   Bit 0: VMXIP, indicates that a virtual interrupt is pending
   delivery, i.e. VMCS.RVI[7:4] > TDVPS.VAPIC.VPPR[7:4]

It also documents how it has to be used.  So this looks more or less 
okay, just rename "vmxip" to "interrupt_pending_delivery".

The VCPU_STATE_DETAILS being "non-architectural" is still worrisome.

Paolo