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Date:   Tue, 18 Dec 2018 07:08:15 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        linux-sgx@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
        Josh Triplett <josh@joshtriplett.org>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Jethro Beekman <jethro@fortanix.com>,
        "Dr . Greg Wettstein" <greg@enjellic.com>
Subject: Re: [RFC PATCH v5 0/5] x86: Add vDSO exception fixup for SGX
Message-ID: <20181218150815.GB28326@linux.intel.com>
References: <20181214215729.4221-1-sean.j.christopherson@intel.com>
 <20181218041815.GA5097@linux.intel.com>
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On Tue, Dec 18, 2018 at 06:18:15AM +0200, Jarkko Sakkinen wrote:
> On Fri, Dec 14, 2018 at 01:57:24PM -0800, Sean Christopherson wrote:
> > __vdso_sgx_enter_enclave() gets another rewrite, this time to strip
> > it down to the bare minimum and explicitly break compliance with the
> > x86-64 ABI.  Feedback from v4 revealed that __vdso_sgx_enter_enclave()
> > would need to save (a lot) more than just the non-volatile GPRs to be
> > compliant with the x86-64 ABI, at which point breaking from the ABI
> > completely became much more palatable.
> > 
> > The non-standard ABI also solves the question of "which GPRs should be
> > marshalled to/from the enclave" by getting out of the way entirely and
> > letting userspace have free reign (except for RSP, which has a big ol'
> > DO NOT TOUCH sign on it).
> 
> Can you share a reference, or is this better documented in the
> accompanied patches?

Patch 5/5 has more details, and v4 of the series has a lot of background
info by way of discussion:

https://lkml.kernel.org/r/20181213213135.12913-1-sean.j.christopherson@intel.com