linux-kernel - Re: [PATCH v19 039/130] KVM: TDX: initialize VM with TDX specific parameters

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Date: Thu, 11 Apr 2024 13:46:29 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"Zhang, Tina" <tina.zhang@...el.com>,
	"isaku.yamahata@...ux.intel.com" <isaku.yamahata@...ux.intel.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>,
	"Huang, Kai" <kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>,
	"sagis@...gle.com" <sagis@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Yuan, Hang" <hang.yuan@...el.com>,
	"Aktas, Erdem" <erdemaktas@...gle.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"Li, Xiaoyao" <xiaoyao.li@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
Subject: Re: [PATCH v19 039/130] KVM: TDX: initialize VM with TDX specific
 parameters

On Thu, Apr 11, 2024 at 07:51:55PM +0000,
"Edgecombe, Rick P" <rick.p.edgecombe@...el.com> wrote:

> On Thu, 2024-04-11 at 12:26 -0700, Isaku Yamahata wrote:
> > > 
> > > So this enables features based on xss support in the passed CPUID, but these
> > > features are not
> > > dependent xsave. You could have CET without xsave support. And in fact
> > > Kernel IBT doesn't use it. To
> > > utilize CPUID leafs to configure features, but diverge from the HW meaning
> > > seems like asking for
> > > trouble.
> > 
> > TDX module checks the consistency.  KVM can rely on it not to re-implement it.
> > The TDX Base Architecture specification describes what check is done.
> > Table 11.4: Extended Features Enumeration and Execution Control
> 
> The point is that it is an strange interface. Why not take XFAM as a specific
> field in struct kvm_tdx_init_vm?

Now I see your point. Yes, we can add xfam to struct kvm_tdx_init_vm and
move the burden to create xfam from the kernel to the user space.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>