From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver Date: Tue, 18 Dec 2018 03:31:44 +0200 Message-ID: <20181218013144.GB333@linux.intel.com> References: <20181116010412.23967-1-jarkko.sakkinen@linux.intel.com> <20181116010412.23967-19-jarkko.sakkinen@linux.intel.com> <7d5cde02-4649-546b-0f03-2d6414bb80b5@intel.com> <20181217180102.GA12560@linux.intel.com> <20181217183613.GD12491@linux.intel.com> <20181217184333.GA26920@linux.intel.com> <20181218011725.GA333@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181218011725.GA333@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski Cc: Dave Hansen , Sean Christopherson , X86 ML , Platform Driver , linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, "Ayoun, Serge" , shay.katz-zamir@intel.com, Haitao Huang , Andy Shevchenko , Thomas Gleixner , "Svahn, Kai" , mark.shanahan@intel.com, Suresh Siddha , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Darren Hart , Andy Shevchenko , open list:X86 ARCHITECTURE (32-BIT AND 64-BIT) List-Id: platform-driver-x86.vger.kernel.org On Tue, Dec 18, 2018 at 03:17:25AM +0200, Jarkko Sakkinen wrote: > On Mon, Dec 17, 2018 at 11:12:21AM -0800, Andy Lutomirski wrote: > > I'm going to ask an obnoxious high-level question: why does an enclave > > even refer to a specific mm? > > The reason is that it has not been yet in focus in the review process > and there has been other concerns. > > At least the code is fairly stable i.e. working code is usually good > starting point for making something different (ignoring the recent > regression caused by the shmem to VMA migration). > > > If I were designing this thing, and if I hadn't started trying to > > implement it, my first thought would be that an enclave tracks its > > linear address range, which is just a pair of numbers, and also keeps > > track of a whole bunch of physical EPC pages, data structures, etc. > > And that mmap() gets rejected unless the requested virtual address > > matches the linear address range that the enclave wants and, aside > > from that, just creates a VMA that keeps a reference to the enclave. > > (And, for convenience, I suppose that the first mmap() call done > > before any actual enclave setup happens could choose any address and > > then cause the enclave to lock itself to that address, although a > > regular anonymous PROT_NONE MAP_NORESERVE mapping would do just fine, > > too.) And the driver would explicitly allow multiple different mms to > > have the same enclave mapped. More importantly, a daemon could set up > > an enclave without necessarily mapping it at all and then SCM_RIGHTS > > the enclave over to the process that plans to run it. > > The current SGX_IOC_ENCLAVE_CREATE ioctl would be trivial to change to > use this approach. Instead looking up VMA with an enclave instance it > would create a new enclave instance. > > Then we could have SGX_IOC_ENCLAVE_ATTACH to attach an enclave to a VMA. > > This does not sound too complicated. > > > Now I'm sure this has all kinds of problems, such as the ISA possibly > > making it rather obnoxious to add pages to the enclave without having > > it mapped. But these operations could, in principle, be done by > > We do EADD in a kthread. What this would require to put current->mm > into a request that it is processed by that thread. This would be > doable with mmget(). Correction here. We need mm just for vm_insert_pfn(), which would be removed, no need to pass mm. /Jarkko