linux-kernel - Re: x86/sgx: uapi change proposal

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Date:   Wed, 19 Dec 2018 18:58:48 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jethro Beekman <jethro@...tanix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        "Dr . Greg Wettstein" <greg@...ellic.com>
Subject: Re: x86/sgx: uapi change proposal

> On Dec 19, 2018, at 6:45 AM, Sean Christopherson <sean.j.christopherson@...el.com> wrote:
>
>> On Wed, Dec 19, 2018 at 09:36:16AM +0000, Jethro Beekman wrote:

> I agree with Jethro, passing the enclave_fd as a param is obnoxious.
> And it means the user needs to open /dev/sgx to do anything with an
> enclave fd, e.g. the enclave fd might be passed to a builder thread,
> it shouldn't also need the device fd.
>
> E.g.:
>
>    sgx_fd = open("/dev/sgx", O_RDWR);
>    BUG_ON(sgx_fd < 0);
>
>    enclave_fd = ioctl(sgx_fd, SGX_ENCLAVE_CREATE, &ecreate);
>    BUG_ON(enclave_fd < 0);
>
>    ret = ioctl(enclave_fd, SGX_ENCLAVE_ADD_PAGE, &eadd);
>    BUG_ON(ret);
>
>    ...
>
>    ret = ioctl(enclave_fd, SGX_ENCLAVE_INIT, &einit);
>    BUG_ON(ret);
>
>    ...
>
>    close(enclave_fd);
>    close(sgx_fd);
>
>
> Take a look at virt/kvm/kvm_main.c to see how KVM manages anon inodes
> and ioctls for VMs and vCPUs.

Can one of you explain why SGX_ENCLAVE_CREATE is better than just
opening a new instance of /dev/sgx for each encalve?