linux-kernel - Re: [PATCH v11 07/20] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <733d0d042f39f099caa35af9b517b6c50ebac12f.camel@intel.com>
Date:   Mon, 5 Jun 2023 23:04:30 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v11 07/20] x86/virt/tdx: Add skeleton to enable TDX on
 demand

On Mon, 2023-06-05 at 14:23 -0700, Isaku Yamahata wrote:
> On Mon, Jun 05, 2023 at 02:27:20AM +1200,
> Kai Huang <kai.huang@...el.com> wrote:
> 
> > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> > index b489b5b9de5d..03f74851608f 100644
> > --- a/arch/x86/include/asm/tdx.h
> > +++ b/arch/x86/include/asm/tdx.h
> > @@ -102,8 +102,12 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
> >  
> >  #ifdef CONFIG_INTEL_TDX_HOST
> >  bool platform_tdx_enabled(void);
> > +int tdx_cpu_enable(void);
> > +int tdx_enable(void);
> >  #else	/* !CONFIG_INTEL_TDX_HOST */
> >  static inline bool platform_tdx_enabled(void) { return false; }
> > +static inline int tdx_cpu_enable(void) { return -ENODEV; }
> > +static inline int tdx_enable(void)  { return -ENODEV; }
> >  #endif	/* CONFIG_INTEL_TDX_HOST */
> >  
> >  #endif /* !__ASSEMBLY__ */
> 
> Please include errno.h.
> In the case of !INTEL_TDX_HOST && INTEL_TDX_GUEST,
> drivers/virt/coco/tdx-guest/tdx-guest.c results in compile error.
> 
> Although there are other files that include asm/tdx.h, they seem to luckily
> include errno.h directly or indirectly.
> 
I've changed to -ENODEV which doesn't cause build error in my test.

I agree it's better to include errno.h explicitly but IMHO it's a problem in the
existing upstream code (tdx_kvm_hypercall() returns -ENODEV when INTEL_TDX_GUEST
is off), thus should be addressed in a separate patch but not folded into this
one.

Since now there's no build error, I hesitated to added such patch.  I can do it
separately if it should be addressed.