linux-kernel - Re: [PATCH] [v2] x86/sgx: Allow enclaves to use Asynchrounous Exit Notification

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Message-ID: <a82e840f-2030-7ab3-7160-f1b900ecdb7d@intel.com>
Date:   Fri, 22 Jul 2022 08:21:46 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Haitao Huang <haitao.huang@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] x86/sgx: Allow enclaves to use Asynchrounous Exit
 Notification

On 7/22/22 06:26, Kai Huang wrote:
> Did a quick look at the spec.  It appears ENCLU[EDECCSSA] should be used
> together with AEX-notify.  So besides advertising the new
> SGX_ATTR_ASYNC_EXIT_NOTIFY bit to the KVM guest, I think we should also
> advertise the ENCLU[EDECCSSA] support in guest's CPUID, like below (untested)?

Sounds like a great follow-on patch!  It doesn't seem truly functionally
required from the spec:

> EDECCSSA is a new Intel SGX user leaf function
> (ENCLU[EDECCSSA]) that can facilitate AEX notification handling...

If that's wrong or imprecise, I'd love to hear more about it and also
about how the spec will be updated.

Oh, and the one-liner patch that I was promised for enabling this is
getting a _wee_ bit longer than one line.