linux-kernel - Re: [PATCH v24 06/24] x86/sgx: Add wrappers for ENCLS leaf functions

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Date:   Thu, 19 Dec 2019 02:39:00 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org, akpm@...ux-foundation.org,
        dave.hansen@...el.com, sean.j.christopherson@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, josh@...htriplett.org, luto@...nel.org,
        kai.huang@...el.com, rientjes@...gle.com, cedric.xing@...el.com,
        puiterwijk@...hat.com
Subject: Re: [PATCH v24 06/24] x86/sgx: Add wrappers for ENCLS leaf functions

On Tue, 2019-12-17 at 15:45 +0100, Borislav Petkov wrote:
> On Sat, Nov 30, 2019 at 01:13:08AM +0200, Jarkko Sakkinen wrote:
> > +/**
> > + * encls_failed() - Check if an ENCLS leaf function failed
> > + * @ret:	the return value of an ENCLS leaf function call
> > + *
> > + * Check if an ENCLS leaf function failed. This happens when the leaf function
> > + * causes a fault that is not caused by an EPCM conflict or when the leaf
> > + * function returns a non-zero value.
> > + */
> > +static inline bool encls_failed(int ret)
> > +{
> > +	int epcm_trapnr =
> > +		boot_cpu_has(X86_FEATURE_SGX2) ? X86_TRAP_PF : X86_TRAP_GP;
> > +	bool fault = ret & ENCLS_FAULT_FLAG;
> > +
> > +	return (fault && ENCLS_TRAPNR(ret) != epcm_trapnr) || (!fault && ret);
> > +}
> 
> Can we make this function more readable?
> 
> static inline bool encls_failed(int ret)
> {
>         int epcm_trapnr;
> 
>         if (boot_cpu_has(X86_FEATURE_SGX2))
>                 epcm_trapnr = X86_TRAP_PF;
>         else
>                 epcm_trapnr = X86_TRAP_GP;
> 
>         if (ret & ENCLS_FAULT_FLAG)
>                 return ENCLS_TRAPNR(ret) != epcm_trapnr;
> 
>         return !!ret;
> }
> 
> I hope I've converted it correctly but I might've missed some corner
> case...
> 
> Thx.

Absolutely. I absolutely hate too "clever code".

/Jarkko