linux-kernel - Re: [PATCH v2 6/8] KVM: TDX: Handle TDG.VP.VMCALL<ReportFatalError>

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Message-ID: <Z6yn2mNYSkhlwtKd@google.com>
Date: Wed, 12 Feb 2025 05:53:30 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: xiaoyao.li@...el.com, pbonzini@...hat.com, kvm@...r.kernel.org, 
	rick.p.edgecombe@...el.com, kai.huang@...el.com, adrian.hunter@...el.com, 
	reinette.chatre@...el.com, tony.lindgren@...el.com, isaku.yamahata@...el.com, 
	yan.y.zhao@...el.com, chao.gao@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/8] KVM: TDX: Handle TDG.VP.VMCALL<ReportFatalError>

On Wed, Feb 12, 2025, Binbin Wu wrote:
> On 2/12/2025 8:18 AM, Sean Christopherson wrote:
> > On Tue, Feb 11, 2025, Binbin Wu wrote:
> > the information is quite useless because userspace doesn't have reg_mask
> > and so can't know what's in data[4], data[5], etc...  And I won't be the
> > least bit surprised if guests deviate from the GHCI.
> 
> But it also confuses userspace if guests uses special protocol to pass
> information other than ASCII byte stream.

Yes, but only if userspace and the guest aren't in cahoots.  There are use cases
where the VMM and the VM are managed/owned by the same entity.