linux-kernel - Re: [PATCH 14/25] KVM: TDX: initialize VM with TDX specific parameters

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Message-ID: <ZtaiNi09UQ1o-tPP@tlindgre-MOBL1>
Date: Tue, 3 Sep 2024 08:44:22 +0300
From: Tony Lindgren <tony.lindgren@...ux.intel.com>
To: Chenyi Qiang <chenyi.qiang@...el.com>
Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>, seanjc@...gle.com,
	pbonzini@...hat.com, kvm@...r.kernel.org, kai.huang@...el.com,
	isaku.yamahata@...il.com, xiaoyao.li@...el.com,
	linux-kernel@...r.kernel.org,
	Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [PATCH 14/25] KVM: TDX: initialize VM with TDX specific
 parameters

On Tue, Sep 03, 2024 at 10:58:11AM +0800, Chenyi Qiang wrote:
> On 8/13/2024 6:48 AM, Rick Edgecombe wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > @@ -543,10 +664,23 @@ static int __tdx_td_init(struct kvm *kvm)
> >  		}
> >  	}
> >  
> > -	/*
> > -	 * Note, TDH_MNG_INIT cannot be invoked here.  TDH_MNG_INIT requires a dedicated
> > -	 * ioctl() to define the configure CPUID values for the TD.
> > -	 */
> > +	err = tdh_mng_init(kvm_tdx, __pa(td_params), &rcx);
> > +	if ((err & TDX_SEAMCALL_STATUS_MASK) == TDX_OPERAND_INVALID) {
> > +		/*
> > +		 * Because a user gives operands, don't warn.
> > +		 * Return a hint to the user because it's sometimes hard for the
> > +		 * user to figure out which operand is invalid.  SEAMCALL status
> > +		 * code includes which operand caused invalid operand error.
> > +		 */
> > +		*seamcall_err = err;
> 
> I'm wondering if we could return or output more hint (i.e. the value of
> rcx) in the case of invalid operand. For example, if seamcall returns
> with INVALID_OPERAND_CPUID_CONFIG, rcx will contain the CPUID
> leaf/sub-leaf info.

Printing a decriptive error here would be nice when things go wrong.
Probably no need to return that information.

Sounds like you have a patch already in mind though :) Care to post a
patch against the current kvm-coco branch? If not, I can do it after all
the obvious comment changes are out of the way.

Regards,

Tony