linux-kernel - Re: RFC: userspace exception fixups

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Date:   Fri, 2 Nov 2018 09:52:04 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jethro Beekman <jethro@...tanix.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rich Felker <dalias@...c.org>, Jann Horn <jannh@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Florian Weimer <fweimer@...hat.com>,
        Linux API <linux-api@...r.kernel.org>, X86 ML <x86@...nel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>,
        "shay.katz-zamir@...el.com" <shay.katz-zamir@...el.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Carlos O'Donell <carlos@...hat.com>,
        "adhemerval.zanella@...aro.org" <adhemerval.zanella@...aro.org>
Subject: Re: RFC: userspace exception fixups

On Fri, Nov 02, 2018 at 04:37:10PM +0000, Jethro Beekman wrote:
> On 2018-11-02 09:30, Sean Christopherson wrote:
> >... The intended convention for EENTER is to have an ENCLU at the AEX target ...
> >
> >... to further enforce that the AEX target needs to be ENCLU.
> 
> Some SGX runtimes may want to use a different AEX target.

To what end?  Userspace gets no indication as to why the AEX occurred.
And if exceptions are getting transfered to userspace the trampoline
would effectively be handling only INTR, NMI, #MC and EPC #PF.