linux-kernel - Re: [PATCH v12 05/13] x86/sgx: architectural structures

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Message-ID: <20180705200912.GA10701@linux.intel.com>
Date:   Thu, 5 Jul 2018 23:09:12 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     x86@...nel.org, platform-driver-x86@...r.kernel.org,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, linux-sgx@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 05/13] x86/sgx: architectural structures

On Thu, Jul 05, 2018 at 08:31:42AM -0700, Dave Hansen wrote:
> On 07/03/2018 11:19 AM, Jarkko Sakkinen wrote:
> > +struct sgx_secs {
> > +	uint64_t size;
> > +	uint64_t base;
> > +	uint32_t ssaframesize;
> > +	uint32_t miscselect;
> > +	uint8_t reserved1[SGX_SECS_RESERVED1_SIZE];
> > +	uint64_t attributes;
> > +	uint64_t xfrm;
> > +	uint32_t mrenclave[8];
> > +	uint8_t reserved2[SGX_SECS_RESERVED2_SIZE];
> > +	uint32_t mrsigner[8];
> > +	uint8_t	reserved3[SGX_SECS_RESERVED3_SIZE];
> > +	uint16_t isvvprodid;
> > +	uint16_t isvsvn;
> > +	uint8_t reserved4[SGX_SECS_RESERVED4_SIZE];
> > +} __packed __aligned(4096);
> 
> Why are the uint* versions in use here?  Those are for userspace ABI,
> but this is entirely for in-kernel-use, right?
> 
> We've used u8/16/32/64 in arch code in a bunch of places.  They're at
> least a bit more compact and easier to read.  It's this:
> 
> 	u8	foo;
> 	u64	bar;
> 
> vs. this:
> 
> 	uint8_t	 foo;
> 	uint64_t bar;

The reason was that with in-kernel LE these were in fact used by
user space code. Now they can be changed to those that you
suggested.

/Jarkko