linux-kernel - Re: [PATCH v29 00/20] Intel SGX foundations

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Message-ID: <ba92f60e41cee1be11b30e8383268b1e1ce896b1.camel@linux.intel.com>
Date:   Thu, 14 May 2020 02:09:19 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jordan Hand <jorhand@...ux.microsoft.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org
Cc:     akpm@...ux-foundation.org, dave.hansen@...el.com,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, bp@...en8.de, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com, puiterwijk@...hat.com
Subject: Re: [PATCH v29 00/20] Intel SGX foundations

On Wed, 2020-05-06 at 09:39 -0700, Jordan Hand wrote:
> On 4/21/20 2:52 PM, Jarkko Sakkinen wrote:
> > Intel(R) SGX is a set of CPU instructions that can be used by applications
> > to set aside private regions of code and data. The code outside the enclave
> > is disallowed to access the memory inside the enclave by the CPU access
> > control.
> > 
> > There is a new hardware unit in the processor called Memory Encryption
> > Engine (MEE) starting from the Skylake microacrhitecture. BIOS can define
> > one or many MEE regions that can hold enclave data by configuring them with
> > PRMRR registers.
> > 
> > The MEE automatically encrypts the data leaving the processor package to
> > the MEE regions. The data is encrypted using a random key whose life-time
> > is exactly one power cycle.
> > 
> > The current implementation requires that the firmware sets
> > IA32_SGXLEPUBKEYHASH* MSRs as writable so that ultimately the kernel can
> > decide what enclaves it wants run. The implementation does not create
> > any bottlenecks to support read-only MSRs later on.
> > 
> > You can tell if your CPU supports SGX by looking into /proc/cpuinfo:
> > 
> > 	cat /proc/cpuinfo  | grep sgx
> > 
> > v29:
> > * The selftest has been moved to selftests/sgx. Because SGX is an execution
> >    environment of its own, it really isn't a great fit with more "standard"
> >    x86 tests.
> > 
> >    The RSA key is now generated on fly and the whole signing process has
> >    been made as part of the enclave loader instead of signing the enclave
> >    during the compilation time.
> > 
> >    Finally, the enclave loader loads now the test enclave directly from its
> >    ELF file, which means that ELF file does not need to be coverted as raw
> >    binary during the build process.
> > * Version the mm_list instead of using on synchronize_mm() when adding new
> >    entries. We hold the write lock for the mm_struct, and dup_mm() can thus
> >    deadlock with the page reclaimer, which could hold the lock for the old
> >    mm_struct.
> > * Disallow mmap(PROT_NONE) from /dev/sgx. Any mapping (e.g. anonymous) can
> >    be used to reserve the address range. Now /dev/sgx supports only opaque
> >    mappings to the (initialized) enclave data.
> > * Make the vDSO callable directly from C by preserving RBX and taking leaf
> >    from RCX.
> > 
> 
> Tested with the Open Enclave SDK on top of Intel PSW. Specifically built 
> the Intel PSW with changes to support /dev/sgx mapping[1] new in v29.
> 
> Tested-by: Jordan Hand <jorhand@...ux.microsoft.com>
> 
> [1] https://github.com/intel/linux-sgx/pull/530

Thank you!

/Jarkko