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

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Message-ID: <bac64e4015b62110d6a0ff2793145856bcfab63c.camel@intel.com>
Date: Tue, 1 Oct 2024 20:45:03 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Qiang, Chenyi" <chenyi.qiang@...el.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>
CC: "seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai"
	<kai.huang@...el.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH 14/25] KVM: TDX: initialize VM with TDX specific
 parameters

On Thu, 2024-09-05 at 12:31 +0300, Tony Lindgren wrote:
> > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > index c00c73b2ad4c..dd6e3149ff5a 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -2476,8 +2476,14 @@ static int __tdx_td_init(struct kvm *kvm, struct
> > td_params *td_params,
> >                   * 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.
> > +                *
> > +                * TDX_OPERAND_INVALID_CPUID_CONFIG contains more info
> > +                * in rcx (i.e. leaf/sub-leaf), warn it to help figure
> > +                * out the invalid CPUID config.
> >                   */
> >                  *seamcall_err = err;
> > +               if (err == (TDX_OPERAND_INVALID |
> > TDX_OPERAND_ID_CPUID_CONFIG))
> > +                       pr_tdx_error_1(TDH_MNG_INIT, err, rcx);
> >                  ret = -EINVAL;
> >                  goto teardown;

Currently we filter by supported CPUID bits. But if we drop that filter and just
allow the TDX module to reject (based on discussion
https://lore.kernel.org/kvm/CABgObfbyd-a_bD-3fKmF3jVgrTiCDa3SHmrmugRji8BB-vs5GA@mail.gmail.com)

...then I guess this could be useful for userspace debugging. I'd say let's
leave this for a follow on patch. It's not critical for now.