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Date:   Sat, 3 Nov 2018 00:42:04 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Jethro Beekman <jethro@fortanix.com>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Rich Felker <dalias@libc.org>, Jann Horn <jannh@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Florian Weimer <fweimer@redhat.com>,
        Linux API <linux-api@vger.kernel.org>, X86 ML <x86@kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "shay.katz-zamir@intel.com" <shay.katz-zamir@intel.com>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Carlos O'Donell <carlos@redhat.com>,
        "adhemerval.zanella@linaro.org" <adhemerval.zanella@linaro.org>
Subject: Re: RFC: userspace exception fixups
Message-ID: <20181102224204.GC24373@linux.intel.com>
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On Fri, Nov 02, 2018 at 09:52:04AM -0700, Sean Christopherson wrote:
> 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.

I've understood that in some cases run-time implementation requires to
run a handler implemented inside the enclave i.e the sequence would be

1. #AEX
2. EENTER(in-enclave handler)
3. EEXIT(%rcx)
4. ERESUME

/Jarkko