linux-kernel - Re: [PATCH v19 035/130] KVM: TDX: Add place holder for TDX VM specific mem_enc

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Message-ID: <a021b0779bd23624bedf7d9b854963fb4edd90ba.camel@intel.com>
Date: Sat, 23 Mar 2024 04:27:42 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "isaku.yamahata@...ux.intel.com"
	<isaku.yamahata@...ux.intel.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"Yuan, Hang" <hang.yuan@...el.com>, "Chen, Bo2" <chen.bo@...el.com>,
	"sagis@...gle.com" <sagis@...gle.com>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>, "Aktas, Erdem" <erdemaktas@...gle.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v19 035/130] KVM: TDX: Add place holder for TDX VM
 specific mem_enc_op ioctl

> 
> > > +
> > > +	mutex_lock(&kvm->lock);
> > > +
> > > +	switch (tdx_cmd.id) {
> > > +	default:
> > > +		r = -EINVAL;
> > 
> > I am not sure whether you should return -ENOTTY to be consistent with the
> > previous vt_mem_enc_ioctl() where a TDX-specific IOCTL is issued for non-TDX
> > guest.
> > 
> > Here I think the invalid @id means the sub-command isn't valid.
> 
> vt_vcpu_mem_enc_ioctl() checks non-TDX case and returns -ENOTTY.  We know that
> the guest is TD.

But the command is not supported, right?

I roughly recall I saw somewhere that in such case we should return -ENOTTY, but
I cannot find the link now.

But I found this old link uses -ENOTTY:

https://lwn.net/Articles/58719/

So, just fyi.