linux-kernel - Re: [PATCH v13 04/13] x86/sgx: Architectural structures

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Date:   Mon, 3 Sep 2018 22:17:56 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        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>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v13 04/13] x86/sgx: Architectural structures

On Mon, Sep 03, 2018 at 04:16:42PM +0300, Andy Shevchenko wrote:
> On Mon, Aug 27, 2018 at 9:57 PM Jarkko Sakkinen
> <jarkko.sakkinen@...ux.intel.com> wrote:
> >
> > Add arch/x86/include/asm/sgx_arch.h, which contains definitions for the
> > architectural data structures used by the CPU to implement the SGX.
> 
> > +/**
> > + * enum sgx_encls_leaves - ENCLS leaf functions
> > + * %ECREATE:   Create an enclave.
> > + * %EADD:      Add a page to an enclave.
> > + * %EINIT:     Launch an enclave.
> > + * %EREMOVE:   Remove a page from an enclave.
> > + * %EDBGRD:    Read a word from an enclve (peek).
> > + * %EDBGWR:    Write a word to an enclave (poke).
> > + * %EEXTEND:   Measure 256 bytes of an added enclave page.
> > + * %ELDB:      Load a swapped page in blocked state.
> > + * %ELDU:      Load a swapped page in unblocked state.
> > + * %EBLOCK:    Change page state to blocked i.e. entering hardware threads
> > + *             cannot access it and create new TLB entries.
> > + * %EPA:       Create a Version Array (VA) page used to store isvsvn number
> > + *             for a swapped EPC page.
> > + * %EWB:       Swap an enclave page to the regular memory. Checks that all
> > + *             threads have exited that were in the previous shoot-down
> > + *             sequence.
> > + * %ETRACK:    Start a new shoot down sequence. Used to together with EBLOCK
> > + *             to make sure that a page is safe to swap.
> > + */
> > +enum sgx_encls_leaves {
> > +       ECREATE = 0x0,
> > +       EADD    = 0x1,
> > +       EINIT   = 0x2,
> > +       EREMOVE = 0x3,
> > +       EDGBRD  = 0x4,
> > +       EDGBWR  = 0x5,
> > +       EEXTEND = 0x6,
> > +       ELDB    = 0x7,
> > +       ELDU    = 0x8,
> > +       EBLOCK  = 0x9,
> > +       EPA     = 0xA,
> > +       EWB     = 0xB,
> > +       ETRACK  = 0xC,
> > +       EAUG    = 0xD,
> > +       EMODPR  = 0xE,
> > +       EMODT   = 0xF,
> > +};
> 
> Hmm... This E prefix confuses me with (system wide) error codes. Has
> it been discussed before? If so, can you point on the conclusion why
> the current format is good?

That is how they are prefixed in the SDM.

> > +enum sgx_miscselect {
> > +       SGX_MISC_EXINFO         = 0x01,
> > +};
> > +
> > +#define SGX_MISC_RESERVED_MASK 0xFFFFFFFFFFFFFFFEULL
> 
> Any idea why we are not using BIT_ULL() / BIT() and GENMASK_ULL() /
> GENMASK() in the code?

No good reason. I'll change it.

> > +enum sgx_attribute {
> > +       SGX_ATTR_DEBUG          = 0x02,
> > +       SGX_ATTR_MODE64BIT      = 0x04,
> > +       SGX_ATTR_PROVISIONKEY   = 0x10,
> > +       SGX_ATTR_EINITTOKENKEY  = 0x20,
> > +};
> > +
> > +#define SGX_ATTR_RESERVED_MASK 0xFFFFFFFFFFFFFFC9ULL
> 
> Some times listing explicitly not-reserved bits might be better and
> figuring out reserved mask is a simple ~ operation.

Yea, agreed.

> > +enum sgx_tcs_flags {
> > +       SGX_TCS_DBGOPTIN        = 0x01,
> > +};
> > +
> > +#define SGX_TCS_RESERVED_MASK 0xFFFFFFFFFFFFFFFEULL
> 
> > +#define SGX_SECINFO_PERMISSION_MASK    0x0000000000000007ULL
> > +#define SGX_SECINFO_PAGE_TYPE_MASK     0x000000000000FF00ULL
> > +#define SGX_SECINFO_RESERVED_MASK      0xFFFFFFFFFFFF00F8ULL
> 
> So, something like
> 
> MASK1 GENMASK_ULL
> MASK2 GENMASK_ULL
> MASK3 ~(MASK1  | MASK2)
> 
> ?

Definitely. I think it is just a matter of legacy why they are like they
are :-) These constants have gone over long time and they are not
usually places where you have to look for regressions. Thanks for
spotting these.

> 
> -- 
> With Best Regards,
> Andy Shevchenko

/Jarkko