linux-kernel - Re: [PATCH v13 07/13] x86/sgx: Add data structures for tracking the EPC pages

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Message-ID: <20180831111038.GA16827@linux.intel.com>
Date:   Fri, 31 Aug 2018 14:10:38 +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,
        Serge Ayoun <serge.ayoun@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Suresh Siddha <suresh.b.siddha@...el.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v13 07/13] x86/sgx: Add data structures for tracking the
 EPC pages

On Tue, Aug 28, 2018 at 09:53:11AM -0700, Dave Hansen wrote:
> >>>  extern bool sgx_enabled;
> >>>  extern bool sgx_lc_enabled;
> >>> +extern struct sgx_epc_bank sgx_epc_banks[SGX_MAX_EPC_BANKS];
> >>> +
> >>> +/*
> >>> + * enum sgx_epc_page_desc - defines bits and masks for an EPC page's desc
> >>
> >> Why are you bothering packing these bits?  This seems a rather
> >> convoluted way to store two integers.
> > 
> > To keep struct sgx_epc_page 64 bytes.
> 
> It's a list_head and a ulong now.  That doesn't add up to 64.

Ah, there used to be one more variable in it.

> If you properly describe the bounds and limits of banks we can possibly
> help you find a nice solution.  As it stands, they are totally opaque
> and we have no idea what is going on.

Great, I see what I can do. I understand now better what you are looking
for. Thanks Dave.

/Jarkko