linux-kernel - Re: [PATCH v4 07/12] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE

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Message-ID: <1a40b4dc8d155618723671685e7ad53e3fce0aa4.camel@intel.com>
Date:   Sat, 26 Aug 2023 00:50:11 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
CC:     "Hansen, Dave" <dave.hansen@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "n.borisov.lkml@...il.com" <n.borisov.lkml@...il.com>
Subject: Re: [PATCH v4 07/12] x86/tdx: Make TDX_HYPERCALL asm similar to
 TDX_MODULE_CALL

On Sat, 2023-08-26 at 02:35 +0300, kirill.shutemov@...ux.intel.com wrote:
> On Tue, Aug 15, 2023 at 11:02:01PM +1200, Kai Huang wrote:
> > +	/*
> > +	 * Failure of __tdcall_hypercall() indicates a failure of the TDVMCALL
> > +	 * mechanism itself and that something has gone horribly wrong with
> > +	 * the TDX module.  __tdx_hypercall_failed() never returns.
> > +	 */
> > +	if (__tdcall_hypercall(TDG_VP_VMCALL, &margs))
> > +		__tdx_hypercall_failed();
> 
> Do we even need __tdx_hypercall_failed() anymore? Just call panic()
> directly, no?
> 

__tdx_hypercall() is currently annotated with 'noinstr' (which is also the
behaviour of the old code).  We need it otherwise we will get build warning like
below:

https://lore.kernel.org/lkml/a23ce8fd289141cea3a1b4f3dace221dca847238.camel@intel.com/T/#m205b29ce3e33983ec6be733c2afffbfd5cb653ff